Part 3

As will be noticed from our list, some insects visit the plants without effecting cross-pollination. Those insects which obtain pollen in an illegitimate manner do not secure it from the small stamens exclusively, but almost invariably visit the large stamen as well.

The adaptation of the plant to propagation by the production of seeds is of considerable significance.[Q]

A normal plant will produce in the neighborhood of 7000 seeds. In making observations on this point, it was found from five pods examined there was an average of fifty-six seeds.

Pod 1 contained 66 seeds. " 2 " 53 " " 3 " 51 " " 4 " 53 " " 5 " 58 " ——— 281 seeds; av., 56.

Pods 4 and 5 were from the same plant but separate racemes; the others were from different plants. In determining the average number of seeds produced by the plant, five plants growing normally and in different localities were observed, with the following results:

Plant 1 192 pods. " 2 50 " " 3 66 " " 4 113 " " 5 210 "

Taking the average of fifty-six seeds per pod obtained above, we see that the plant producing 122.5 pods, the average from the preceding table, would produce about 7000 seeds.

One plant was observed upon which occurred fifty-five to sixty racemes. Allowing the low average of six pods to the raceme, the plant will produce in the neighborhood of 20,000 seeds. Occasionally a very large plant is observed which produces as many as 125 racemes. Allowing the same low average of six pods to the raceme, it will be seen that on a plant of this size there will be produced in the neighborhood of 40,000 seeds.

Only a very small proportion of the ovaries fail to develop. Out of the forty-one racemes observed in five plants, taken at random in different localities, results were obtained as follows:

Plant 1, 5 racemes, 53 pods, 4 failed. " 2, 5 " 42 " 3 " " 3, 9 " 55 " 5 " " 4, 11 " 91 " 6 " " 5, 11 " 121 " 5 " —— ——— —— 41 racemes, 367 pods, 23 failed, or 6.2 per cent.

According to these figures, not more than 6.2 per cent. of the ovaries failed to be fertilized.

While _Cassia chamæcrista_ is usually abundant in Douglas county, owing, probably, largely to the severe drought, opportunities for study were not nearly so favorable as for _Solanum_. The material studied was found growing, for the most part, in somewhat shaded localities on the banks of Lake View.

Professor Todd has given very well the points in the structure of the flower of this species. He says: “The points that are of interest to us are the sickle-shaped pistil, the stamens with long, rigid anthers opening by terminal pores, and the most of them pointed toward the incurved petal, which is always on the opposite side from the pistil.”

The flowers are arranged in small clusters a little above the axils of the leaves. In some cases the axillary bud also develops into a flower cluster. The axillary clusters have been considered separately in the calculations made upon the conditions of the flowers.

Owing to the lack of material, Professor Todd was unable to determine any definite law governing the arrangement of the flowers in _C. chamæcrista_. This the writers have attempted to do. The determination of any law governing the order of development of the flowers in a plant like _C. chamæcrista_, where they are arranged in clusters developed from buds produced on the main axis, and the development of which is probably accelerated or retarded by various conditions, is much more difficult than in _S. rostratum_, where they are produced on a definite raceme, which is early differentiated from the terminal growing point, and at first develops more rapidly than the bud which is to continue the main axis of the branch.[R]

TABLE D. (Part 1)

═════════╤═════════╤═════════╤═════════╤═════════╤═════════╤═════════╕ _Cluster_ │ 1 │ 2 │ 3 │ 4 │ 5 │ 6 │ ─────────┼─────────┼─────────┼─────────┼─────────┼─────────┼─────────┤ PLANT. │ │ │ │ │ │ │ { 1 │ A │ 2b │ b, 5p │ b, l, p │ A │ A │ I { 2 │ l, p │ 2p │ A │ 3p │ p │ A │ { │ │ │ │ │ │ │ { 3 │ p │ 3p │ 4p │ b, 3p │ br, 4p │ b, r, p │ │ │ │ │ │ │ │ II—1 │ 2b │b, 3p, a │b, 2p, a │ 2b, 3p │ 2b, 3p │ r │ │ │ │ │ │ │ │ III—1 │ 3b │ 2b, p │ b, 2p │ 2b, 2p │ b, br, p│ b, 3p │ │ │ │ │ │ │ │ { 1 │ b │ 2b, bl │ 2b, r │ 2b, bl │ 3b │ 3b, br │ IV{ 2 │ A │ b, bl │ 3b, bl │ 3b, p │ 3b │3b, r, p │ │ │ │ │ │ │ │ V—1 │ A │ 2b, p │ b, 1, p │ b, p │ b, r, p │ 2b, 2p │ │ │ │ │ │ │ │ { 1 │ A │ A │ A │ A │ p │ 2p, a │ VI{ 2 │ A │ p │ b, 3p │ b, 2p │ 2b, 3p │ 2b, p │ │ │ │ │ │ │ │ VII—1 │b, bl, 2p│ 2b, 2p │ b, l, p │2b, bl,2p│ b, r, 2p│2b, br, p│ │ │ │ │ │ │ │ { 1 │ 2b │ 2b │ 2b │ 2b │ 2b │ │ VIII{ │ │ │ │ │ │{ 2b, l │ { 2 │ b │ 2b, 1p │ b, l, p │ 2b, r, p│ 3b, br │{ b │ │ │ │ │ │ │ │ { 1 │ 2p │b, br, 2p│ absent │ 2b, 3p │ b, r, 2p│ 2b, a │ { 2 │ b, 3p │ 2b, 4p │ b, l, 3p│ 2b, 2p │ b, 3p │2b, bl,2p│ IX{ 3 │ A │ 2b, 3p │ 2b, p │ 2b, p, a│ 2b, 3p │ 2b, p │ { 4 │ A │ b, 2p │ b, p │ b, r, 2p│ b, 3p │ b, p, a │ │ │ │ │ │ │ │ { 1 │ 2b, 1p │ 2b │ 2b, p │ b, 2p │ br, p │ b, br, p│ X{ 2 │ A │ A │ b │ b, a │ b, p │ 2b, p │ ─────────┴─────────┴─────────┴─────────┴─────────┴─────────┴─────────┘

TABLE D. (Part 2)

═════════╤═════════╤═════════╤══════════╤═════════╤════════╤═════════╕ _Cluster_ │ 7 │ 8 │ 9 │ 10 │ 11 │ 12 │ ─────────┼─────────┼─────────┼──────────┼─────────┼────────┼─────────┤ PLANT. │ │ │ │ │ │ │ { 1 │ A │ A │ A │ b, 2p │ 2b, 2p │ 2b, 2p │ I { 2 │ A │ 2b, lp │ b │ A │ 3b, p │{ 2b │ { │ │ │ │ │ │{ lb │ { 3 │ b, 4p │2b, bl,3p│2b,br,2p,a│ 2b, p, a│b, l, 2p│2b, bl, p│ │ │ │ │ │ │ │ II—1 │ 2b, br │ 2b, br │ b, r, p │ 2b, bl │ 3b │ 2b │ │ │ │ │ │ │ │ III—1 │ b, 3p │ 4p │ b, r, 3p │ b, bl,3p│ b, 3p │ 3b, 2p │ │ │ │ │ │ │ │ { 1 │ 2b, l │ 3b │ 3b │ 3b │ 3b │ 3b │ IV{ 2 │ 3b, br │ 3b, l │ 4b │ 4b │ 4b │ │ │ │ │ │ │ │ │ V—1 │b, bl, p │ b, r, p │ 2b, r │ 2b │ 2b │ 2b │ │ │ │ │ │ │ │ { 1 │ b, 3p │ b, 3p, a│ b, r, 3p │ 2b, 2p │ 2b, 3p │ 3b, p │ VI{ 2 │ b, r, p │ 2b, p, a│ 2b, l, p │ 3b, p │ 3b, r │ 3b │ │ │ │ │ │ │ │ VII—1 │{2b, l, p│ 3b, bl │{ 3b, r │ 3b │ 3b │ 3b │ │{ 2b │ │{ b │ │ │ │ { 1 │ │ │ │ │ │ │ VIII{ │ 3b │ 3b │ │ │ │ │ { 2 │ 2b │ b │ │ │ │ │ │ │ │ │ │ │ │ { 1 │ 2b, bl │ 2b, r, p│ 2b, a │ 2b, l │ 3b │ 2b │ { 2 │ 2b, r │ 2b, p │ b, l, p │ 2b, bl │ 3b │ 3b │ IX{ 3 │ b, 2p │ l │ 2b, 2p │b, br, 2p│ 2b, 2p │ 2b │ { 4 │ b, r, 3p│ b, 3p │ │ │ │ │ │ │ │ │ │ │ │ { 1 │ b, bl, r│ 2b, br │ 2b │ 2b │ 2b │ b, a │ X{ 2 │ b, r │ 2b, a │ l │ 2b │ 2b │ │ ─────────┴─────────┴─────────┴──────────┴─────────┴────────┴─────────┘

TABLE D. (Part 3)

═════════╤═════════╤═════════╤═════════╤═════════╤═════════╤═════════╕ _Cluster_ │ 13 │ 14 │ 15 │ 16 │ 17 │ 18 │ ─────────┼─────────┼─────────┼─────────┼─────────┼─────────┼─────────┤ PLANT. │ l │ b, 2p │ 2b, 2p │ 3b, 2p │{ 3b, p │br, 2b, p│ { 1 │ │ │ │ │{ b │ b │ I { 2 │ 3b, p │ 2b, l, p│ 2b, bl │ 2b, r │{ 3b │ 2b │ { │ │ │ │ │{ b │ │ { 3 │ br, a │{2b, br,a│ 2b, la │ 2b │ b │ 2b │ │ │{ b │ │ │ │ │ II—1 │ 2b │ │ │ │ │ │ │ │ │ │ │ │ │ III—1 │ b, 3p │ 2b, bl │ 2b, p │ 2b, r │ b │ b │ │ │ │ │ │ │ │ { 1 │ │ │ │ │ │ │ IV{ 2 │ │ │ │ │ │ │ │ │ │ │ │ │ │ V—1 │ │ │ │ │ │ │ │ │ │ │ │ │ │ { 1 │ │ │ │ │ │ │ VI{ 2 │ 3b, a │ 3b, a │ 2b, l │ 3b │ 3b │ 3b │ │ │ │ │ │ │ │ VII—1 │ 3b │ 3b │ 2b │ │ │ │ │ │ │ │ │ │ │ { 1 │ 2b │ 2b │ │ │ │ │ VIII{ │ │ │ │ │ │ │ { 2 │ │ │ │ │ │ │ │ │ │ │ │ │ │ { 1 │ │ │ │ │ │ │ { 2 │ │ │ │ │ │ │ IX{ 3 │ │ │ │ │ │ │ { 4 │ │ │ │ │ │ │ │ 3b │ │ │ │ │ │ { 1 │ │ │ │ │ │ │ X{ 2 │ 2b, p │ 2b, a │ 3b │ 2b │ │ │ ─────────┴─────────┴─────────┴─────────┴─────────┴─────────┴─────────┘

TABLE D. (Part 4)

═════════╤═════════╤═════════╤═════════╤═════════╤═════════╤═════════╕ _Cluster_ │ 19 │ 20 │ 21 │ 22 │ 23 │ 24 │ ─────────┼─────────┼─────────┼─────────┼─────────┼─────────┼─────────┤ PLANT. │ 3b, p │{ 2b, br │ 3b │ { 3b │ │ │ { 1 │ │{ b │ │ { b │ │ │ { │ 2b │ │ │ │ │ │ { 3 │ │ │ │ │ │ │ │ │ │ │ │ │ │ II—1 │ │ │ │ │ │ │ │ │ │ │ │ │ │ III—1 │ │ │ │ │ │ │ │{ 2b, 2p │ b, l, p │{ 2b, l │ 3b, a │ 2b, a │ 2b │ { 1 │ b │ │ b │ │ │ │ IV{ 2 │ │ │ │ │ │ │ │ │ │ │ │ │ │ V—1 │ │ │ │ │ │ │ │ │ │ │ │ │ │ { 1 │ │ │ │ │ │ │ VI{ 2 │ │ │ │ │ │ │ │ │ │ │ │ │ │ VII—1 │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ { 1 │ │ │ │ │ │ │ VIII{ │ │ │ │ │ │ │ { 2 │ 3b │ │ │ │ │ │ │ │ │ │ │ │ │ { 1 │ │ │ │ │ │ │ { 2 │ │ │ │ │ │ │ IX{ 3 │ │ │ │ │ │ │ { 4 │ │ │ │ │ │ │ │ │ │ │ │ │ │ { 1 │ │ │ │ │ │ │ X{ 2 │ │ │ │ │ │ │ ─────────┴─────────┴─────────┴─────────┴─────────┴─────────┴─────────┘

TABLE D. (Part 5)

═════════╤══════════════════════════════════╕ _Cluster_ │ │ ─────────┼──────────────────────────────────┤ PLANT. │ │ { 1 │ 6A, 35b, 2br, 2l, 21p. │ { │ 4A, 26b, 1bl, 2l, 1r, 11p. │ { 3 │ 23b, 2bl, 4br, 1l, 1r, 31p, 5a. │ │ │ II—1 │ 22b, 2br, 1bl, 2r, 12p, 2a. │ │ │ III—1 │ 41b, 2bl, 1br, 2l, 2r, 34p, 2a. │ │ │ { 1 │ 30b, 2bl, 1br, 1l, 1r, 2p. │ IV { 2 │ 1A, 31b, 2b1, 1br, 1l, 1r, 2p. │ │ │ V—1 │ 1A, 17b, 1bl, 1l, 3r, 8p. │ │ │ { 1 │ 4A, 30b, 1l, 1r, 18p, 4a. │ VI { 2 │ 1A, 28b, 1l, 2r, 14p, 1a. │ │ │ VII—1 │ 33b, 3bl, 1br, 2l, 2r, 11p. │ │ │ { 1 │ 10b. │ VIII { 2 │ 21b, 1br, 2l, 1r, 3p. │ │ │ { 1 │ 19b, 1bl, 1br, 1l, 2r, 10p, 2a. │ { 2 │ 25b, 2bl, 2l, 1r, 19p. │ IX { 3 │ 1A, 27b, 1br, 1l, 18p, 2a. │ { 4 │ 1A, 7b, 2r, 15p, 1a. │ │ │ { 1 │ 18b, 1bl, 3br, 1r, 6p, 1a. │ X { 2 │ 2A, 12b, 1l, 1r, 2p, 2a. │ ├──────────────────────────────────┤ │ 21A, 455b, 18br, 18bl, 21l, 24r, │ │ 234p, 22a. │ ─────────┴──────────────────────────────────┘

Abundant material in apparently the best condition was found growing around Lake View. Ten plants from this locality were examined, and their condition is here given in tabulated form. In the table following, the number of the plant is given in Roman numerals, the numbers of the branches following it in Arabic numerals. Beginning with the lower portion of the branch and passing upward, the flower clusters are numbered consecutively. These numbers, designated by “cluster,” are given in the first line at the top of the table. In the column beneath each of these numbers is shown the condition of the flowers of that cluster on the different branches of the different plants. The table was arranged in this form, not because a comparison of the condition of clusters of the same number is especially desired, but because this seemed the most compact form in which it could be arranged. In the columns under the different clusters, the condition of the flowers is designated as follows: _r_ = right-, _l_ = left-handed flower; _b_ = bud; _br_ and _bl_ designate buds which are so well developed that it is possible to determine whether they are right-handed or left-handed—these buds will probably open the following morning; a = a bud or flower which has fallen off or failed to develop; A, indicates that the whole cluster has failed to develop. When an axillary cluster is developed it is included in a brace, with the cluster occurring immediately above it, the axillary cluster always being placed below. A seed pod is designated by _p_.

In the last column to the right the condition of each branch is summarized, and finally the grand total is given at the foot of the column.

In table D we have taken into account 241 flower clusters, and 21 which are either abortive or injured. The number of abortive clusters might be somewhat increased if great care had been exercised in looking for the accessory buds just above the axils of the lowest leaves on the branches. As a rule, however, the first internode or so, if questionable, was omitted. From this it would seem that about eight per cent. of the clusters fail to develop, a percentage which would probably be somewhat increased if care had been exercised in noting the buds where development had been arrested at a very early stage.

On the 10 plants, 14 axillary clusters were produced, being 5.5 per cent. of all the developed clusters. Of these 14 clusters, 2 produced 2 buds each, the others only 1; an average of 1.14 flowers per cluster. The 241 normally developed clusters produced 773 buds, an average of 3.27 flowers per cluster. Of the 773 buds produced on the 10 plants, 22 are found to be injured and fail to develop normally; a percentage of 2.84.

While the series of material is too limited to permit of indulging in generalizations, it might be of interest to note that on 40 plants bearing 332 seed pods, taken from two square feet of ground, September 4, and 3 other plants producing 130 seed pods, taken at the same time, not a single pod developed from an axillary cluster was found. These plants, however, with the exception of the last three, represent all produced on a definite area. It might not be improbable that the smaller, crowded plants would not be so likely to produce axillary clusters as the larger plants growing under more favorable conditions. We may at least conclude from this that the axillary flowers are of little consequence in the seed-producing capacity of the plant.

For the sake of convenience, it has been deemed advisable to summarize in table E the conditions of the flowers and buds which will probably open the day following, as given in table D. From this table, it will be seen that on the day the plants were examined 42 flowers were open—5.4 per cent. of the 773 buds produced on the 10 plants. These flowers as well as the buds, 36 in number, which were to open the next day, are equally divided into right-and left-handed.

The buds which are next to open do not, in any of the cases noted in the above tables, occur on a cluster with flowers which are already open.

TABLE E.

Plant I, 6_r_ buds, 3_l_ buds, 2_r_ flowers, 5_l_ flowers. II, 2_r_ " 1_l_ " 2_r_ " 0_l_ " III, 1_r_ " 2_l_ " 2_r_ " 2_l_ " IV, 2_r_ " 4_l_ " 2_r_ " 2_l_ " V, 0_r_ " 1_l_ " 3_r_ " 1_l_ " VI, 0_r_ " 0_l_ " 3_r_ " 2_l_ " VII, 1_r_ " 3_l_ " 2_r_ " 2_l_ " VIII, 1_r_ " 0_l_ " 1_r_ " 2_l_ " IX, 2_r_ " 3_l_ " 5_r_ " 4_l_ " X, 3_r_ " 1_l_ " 2_r_ " 1_l_ " —— —— —— —— 18_r_ buds, 18_l_ buds, 24_r_ flowers, 21_l_ flowers.

There seems to be no law governing the production of right-and left-handed flowers on the opposite sides of the main axis of the plant. Sometimes two right-or left-handed flowers will be produced in succession on one side of the raceme, and sometimes right-and left-handed alternate on the same side.

Concerning the method of pollination in _C. chamæcrista_, the writers have not been able to thoroughly satisfy themselves. Todd says: “I consider the following explanation most probable: In getting the pollen, some grains are dropped on the incurved petal, and by it made to adhere to points of the bee, and to such points in a right-handed flower as will carry it to the stigma of a left-handed flower, and _vice versa_.” Robertson[S] says: “The pollen, being thus forced out of the terminal anther pores, falls either directly upon the bee or upon the lateral petal which is pressed close against the bee’s side. In this way the side of the bee which is to the incurved petal receives the most pollen.... A bee visiting a left-hand flower receives pollen upon the right side and then flying to a right-hand flower strikes the same side against the stigma.”

It is very difficult to see just what takes place when the flowers are visited by a large insect, but the writers have observed that when they are visited by honey-bees, for instance, the insect supports itself by hooking his left hind leg over the terminal, upturned portion of the stigma in a right-handed flower, and the right leg in a left-handed flower. The pistil then would serve the function of support for the insect visitor. It was noticed that sometimes bees would attempt to get the pollen by approaching the flower from some direction other than that described above. The insect usually failed in this, and after one or two unsuccessful endeavors would give up the attempt and support itself by placing the leg over the terminal portion of the pistil while it secured the pollen. The function of the incurved petal is not perfectly clear. With an insect well dusted over with pollen from both right-and left-handed flowers, it seems improbable that cross-fertilization in any considerable number of cases should occur from some grains dropped on the incurved pistil.