The series of experiments upon which this paper is based were conducted in a greenhouse by the writers during the winter of 1896-1897. Seeds of the following plants were employed: Garden peas, beans, soja (soy) beans, hairy vetch, rye, barley, wheat, and oats, the three first named being principally delt with here. In all cases except that of the hairy vetch the seed was of known origin, each variety having come from a single lot grown in one place. We consider this fact one of the most important conditions of the experiment. In many experiments on record of somewhat similar nature no mention is made of the origin of the seed, which is generally of the ordinary commercial kind and often a mixture of various lots grown under different conditions. The results obtained from such seed can not be relied upon.
The seed was carefully separated into two lots, one of heavy the other of light seed, the individual seeds of each lot having approximately the same weight. These seeds were planted in pure sand, and the plants were given equal amounts of a culture solution which contained all the necessary elements of plant food. They were kept from first to last under identically similar conditions so far as possible, measurements and photographs being made from time to time. At the conclusion of each experiment typical plants from each lot were photographed, carefully taken from the soil, weighed, and measured.
The table following shows the comparitive growth of soja beans from heavy and light seed. The seed used in this experimehnt was raised at the Massachusetts Agricultural Experiment Station. It was planted September 15, 1896, and harvested December 12, a growing period of eighty-eight days.
| (a) FIVE HEAVY SEEDS | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| plant number | Weight in Grams1 | height | leaves | taproot | stem diam. | ||||
| plant | seed | root | shoot | ||||||
| 2 . . . . | (.189) | 4.8 (0.7) | 8.6 (3.3) | 13.4 (4.0) | 352mm | 17 | 220mm | 4.0mm | |
| 5 . . . . | (.204) | 4.0 (.6) | 9.7 (6.7) | 14.3 (7.3) | 405mm | 19 | 238mm | 4.0mm | |
| 6 . . . . | (.201) | 5.8 (.9) | 9.7 (3.8) | 15.5 (4.7) | 407mm | 28 | 215mm | 4.5mm | |
| 7 . . . . | (.219) | 3.8 (.6) | 7.4 (2.6) | 11.2 (3.2) | 415mm | 24 | 202mm | 3.5mm | |
| 10. . . . | (.197) | 12.1 (1.2) | 19.6 (6.6) | 31.7 (7.8) | 438mm | 26 | 198mm | 5.0mm | |
| Total . . . | (1.010) | 31.10 (4.0) | 55.0 (23.0) | 86.1 (27.0) | 2,062mm | 114 | 1,073mm | 21.0mm | |
| Average . . | (.202) | 6.22 (0.8) | 11.0 (4.6) | 17.22 (5.4) | 212.4mm | 22.8 | 214.6mm | 4.2mm | |
| (a) FIVE LIGHT SEEDS | |||||||||
| plant number | Weight in Grams1 | height | leaves | taproot | stem diam. | ||||
| plant | seed | root | shoot | ||||||
| 12. . . . | (.077) | 3.9 (.4) | 6.3 (2.4) | 10.2 (2.8) | 261mm | 15 | 352mm | 3.0mm | |
| 14. . . . | (.088) | 2.0 (.2) | 4.8 (2.0) | 6.8 (2.2) | 281mm | 13 | 180mm | 3.0mm | |
| 16. . . . | (.085) | 1.2 (.2) | 2.5 (.8) | 3.7 (1.0) | 157mm | 11 | 195mm | 2.5mm | |
| 17. . . . | (.076) | 8.0 (.7) | 11.7 (4.0) | 19.7 (4.7) | 343mm | 18 | 375mm | 4.0mm | |
| 18. . . . | (.086) | 2.7 (.4) | 6.9 (3.0) | 9.6 (3.4) | 344mm | 11 | 182mm | 3.0mm | |
| Total . . . | (.412) | 17.8 (1.9) | 32.2 (12.2) | 50.0 (14.1) | 1,386mm | 68 | 1,284mm | 15.5mm | |
| Averge . . | (.082) | 3.56 (.4) | 6.44 (2.44) | 10.0 (2382) | 277.2mm | 13.6 | 256.8mm | 3.1mm | |
| 1The weights are: fresh, (air dry). | |||||||||
| SUMMARY | |||||||||
| plant number | Weight in Grams1 | height | leaves | taproot | stem diam. | ||||
| plant | seed | root | shoot | ||||||
| Total Heavy | (1.010) | 31.10 (4.0) | 55.0 (23.0) | 86.1 (27.0) | 2,062mm | 114 | 1,073mm | 21.0mm | |
| Average Heavy | (.202) | 6.22 (0.8) | 11.0 (4.6) | 17.22 (5.4) | 212.4mm | 22.8 | 214.6mm | 4.2mm | |
| Total Light | (.412) | 17.8 (1.9) | 32.2 (12.2) | 50.0 (14.1) | 1,386mm | 68 | 1,284mm | 15.5mm | |
| Averge Light | (.082) | 3.56 (.4) | 6.44 (2.44) | 10.0 (2382) | 277.2mm | 13.6 | 256.8mm | 3.1mm | |
A reference to the table shows that the heavy seed (lot a) weighed over twice as much as the light (lot b), and the resulting plants weighed nearly twice as much in the former case as in the latter.
The development of the soja beans was retarded for a couple of weeks by unavoidable lowering of the temperature in the greenhouse. Afterwards the growth was uninterrupted and the plants at all times were healthy, although the ususal somewhat bushy habit of similar plants in the field was not attained. No root tubercles were developed, with the exception of a few on No. 12. The experiment was closed at a time when the plants were in the best condition for forage or green manure, that is, about the time of flowering. It is not known, however, whether this degree of difference would have been maintained in the open field. Hellriegel claims that the difference between mature plants from large and small seed is greater in impoverished soil than in that which is richly supplied with food material. The difficulty of absolutely controlling the conditions of plants in the field makes results from such experiments somewhat uncertain. Although no organized food was furnished to the soja beans in this experiment, an abundant amount of all the elements necessary to plant growth was constantly given them. The plants of each lot were treated alike and the results obtained hold perfectly good for comparison, although the greenhouse conditions were not as favorable as could have been wished and the total development was much smaller than it would have been in the open field, where it is believed a greater difference would have been shown in the result.
It has also been stated by Hellriegel that the differences in plants grown from large and small (in this case equivalent to heavy and light) seed are most apparent in their earlier stages, growing less marked toward maturity. He further claims that a greater difference at maturity is visible in plants grown in quartz-sand cultures than those grown in garden soil. The curves shown in figure 74 are of great interest as bearing on this point. It will be noticed that, while the two plants of each lot maintained an approximately equal growth throughout this experiment, during the early seedling stage - that is \, for the first week from the time of planting - the plants from both heavy and light seed showed nearly the same degree of development. From this period the growth of the two lots began to deviate considerably, reaching its widest diergence at the close of the experiment. Fig 75 is taken from photographs, one made thirty days from the time of planting and the other at the close of the experiment. In both cases a striking difference is shown in the development of the plants from the two kinds of seed. The same difference between seedlings of soja beans from heavy and light seed is seen in fig. 76,II, which represents a typical seedling from a lot of heavy and another from light seed. The difference in development is equally apparent in roots, stems, and leaves. A study of the individual plants (see table above) shows that each plant (fresh) in lot b was lighter than any of lot a, excepting No. 17. In this case the large weight is unaccountable. The pot in which this plant grew proved to be less porous and hence more retentive of moisture than any of the rest, and to this fact some of the extra vigor may have been due. Plant No. 16 , from some unknown cause, showed a retarded development from the first, and was lightest at the close of the experiment. However, the extra development of one plant is nearly ofset by the weakness of the other, and the average result is only slightly affected, although the difference in favor of the heavy seed would have been more marked if these plants had not been taken into account. It will be observed that while the weight of each plant is not exactly proportional to that of the seed, there is an unmistakable average proportion maintained in considering the total of each lot.
Plants from the heavier seed were greater not only in weight, but also in length, in number of leaves, and in diameter of stem. Although the average root length was greater in the soja beans grown from light seed, the total root development was much less. The advantage to the heavy seed plants in possessing a greater root development is evident in the fact that such plants have so many more absorbing organs for taking up the food elements from the soil. Another great advantage, especially while in the seedling stage, is in the better soil grasp afforded to such plants, giving them a firmer hold at a period when the wind or other unfavorable circumstance is most likely to uproot them or lay bare their roots. The greater stem diameter is correlated with a larger number of tubes (vascular bundles) for pumping up the nourishment to various portions of the plant. The larger leaf surface secures greater transpiration and consequently a more rapid food supply, as well as a greater capacity for transforming the raw food materials into the organized substances necessary for growth.