SEEDS 



5291 



SEEDS 



divisions in accordance with these plans. When 

 a bean or a squash seed germinates, two thick 

 leaves shaped like the halves of the seed are 

 the first objects to appear above the ground. 

 Between them, we see the tiny plant ready to 

 put forth its leaves. The two thick leaves con- 

 tain the food for the embryo, and when the 

 food has been absorbed by the growing plant- 



FIG. 1 



(a) Cross section of a grain of corn ; (&) cross 

 section of asparagus seed; (c) cross section of 

 squash and .one carpel ; (d) common bean, split 

 open; (e) cross section of onion seed. 



let they wither and fall. They are known as 

 seed leaves, or cotyledons, a name which comes 

 from a Greek word meaning hollow or cuplike. 



When corn germinates no seed leaves appear 

 above the ground, the first leaf being the tiny 

 shoot which unfolds into the young corn plant. 

 If we look at the kernel of corn (a, Fig. 1), we 

 see that the embryo is surrounded by plant 

 food upon all sides. We cannot divide the corn 

 into halves as we can the bean, because this 

 food is all stored in one mass. That is, the 

 corn has only one seed leaf, or cotyledon. All 

 plants having seeds with only one cotyledon 

 are called monocotyledonous plants. Corn, 

 wheat, oats, barley and grasses are good ex- 

 amples of plants belonging to this division. 



We have seen that the bean and squash pro- 

 duce seeds with two seed leaves. All plants 



FIG. 2 



(a) Lengthwise section of a pansy seed; (b) 

 lengthwise section of a buttercup seed; (c) cap- 

 sule of violet, split open, showing seeds attached 

 to placentae; (d) cross section of iris capsule; 

 (e) lengthwise section of poppy seed. 



with seeds having two seed leaves are called 

 dicotyledonous plants. The maple, elm, oak, 

 alfalfa and clover, besides the other plants 

 named, are good examples of this division. 

 Cone-bearing trees produce seeds with more 

 than two seed leaves and form the division of 

 polycotyledonous plants. One needs to know 

 the meaning of these terms because they are 



frequently met with in reading botanical de- 

 scriptions of plants. 



A study of the arrangement of seeds in the 

 seed vessel or fruit leads to some of the most 

 curious and interesting facts connected with 

 the study of plants. How many can tell the 

 direction in which the seeds of the apple point? 

 (See a, Fig. 3.) Does the pit of the peach point 

 in the same direction? (See e, Fig. 3.) Notice 

 how the seeds are arranged in the squash (c, 

 Fig. 1); in the iris (d, Fig. 2), and in the 

 cranberry (d, Fig. 3). In the blackberry (c, 

 Fig. 3), they are attached to the outside of a 

 fleshy receptacle, but each seed is enclosed in 

 a little, pulpy fruit. In the strawberry the seed 

 is on the outside of the fleshy receptacle. No- 

 tice the ingenious method by which the seeds 

 are packed into these capsules or pods. By no 

 other arrangement could the same number of 



FIG. 3 



(a) Lengthwise section of apple, showing posi- 

 tion of seeds in center; (&) lengthwise section of 

 cherry, with seed in center; (c) lengthwise sec- 

 tion of part of blackberry; (d) cross section of 

 cranberry; (e) lengthwise section of peach, 

 showing seed in center. 



seeds be crowded into the space. Make a col- 

 lection of seed vessels before they open and 

 observe the arrangement of the seeds in each. 



Seed Adulteration. The seeds of some culti- 

 vated plants so closely resemble those of worth- 

 less plants that these seeds may be mixed and 

 no one but an expert can detect the fraud. To 

 illustrate, the seeds of pepper grass, dodder, 

 crab grass and sorrel may be mixed with timo- 

 thy seed, and kale and mustard may be mixed 

 with turnip seed. It is difficult to obtain pure 

 seed for planting because weeds grow with the 

 crop and are necessarily harvested with it. 

 While most of the weed seeds are separated 

 from the grain at threshing, some remain, and 

 if sowed the next season they produce another 

 crop of weeds. A large number of fanning 

 mills have been invented for the purpose of 

 enabling the farmer to obtain pure seed for 

 planting. 



Seed Testing. The importance of securing a 

 good crop makes it advisable for the farmer to 

 test his seed before planting. A simple device 

 consists of two plates of the same size. Lay 

 a piece of blotting paper in one plate, first 

 marking it off into squares two inches in diame- 



