46 



SEEDS AND SEEDLINGS. 



78. Culinary Pea (Pisum sativum) and Sweet Pea 



(Lathyrus odoratus). In the former, note through the 

 transparent coat of a soaked seed the scar, micropyle, and 

 root, all lying in the same line with the root-tip pointing to 

 the micropyle; the cotyledons are hypogeal; the earlier 

 leaves are small and like those of the Broad Bean seedling ; 

 the later leaves differ in that the uppermost leaflets are 

 developed as tendrils. In Sweet Pea, note the foliage-leaves 

 have only two leaflets; in what other respects does this 

 seedling differ from that of the Culinary Pea ? 



79. Oak, Sycamore, Sunflower. To make a thorough 

 study of the akenes or " seeds " of these plants, you should 

 get the flowers of each plant, with ripe and unripe fruits. 



G-et ripe Oak acorns, also unripe ones still attached to 

 the cup, noting the scar at base of acorn where it was fixed 

 inside the cup ; the withered style with its three stigmas at 

 the free pointed end of the acorn ; 

 the hard shell (fruit- wall) and the 

 thin skin (seed-coat) inside it; the 

 two large cotyledons, the root, and 

 the small plumule; the abundant 

 starch stored in the cotyledons ; the 

 splitting of the shell on germination 

 and the pushing out of the young 

 root and shoot by elongation of the 

 cotyledon- stalks (Fig. 23). 



Get Sycamore "keys," which are 

 at first joined in pairs (sometimes 

 in threes), each having a wing. 

 Watch the keys being blown from 

 the tree on a windy day, noting their 

 spinning or whirling movement 

 through the air. What makes the 

 keys whirl, are they carried far from 



the tree, and does the whirling enable them to bore into soft 

 moist soil ? Throw keys into the air or drop them from a 

 height ; repeat the experiment with keys from which the wing 

 has been removed, comparing the times taken for winged and 

 wingless keys to fall through the same distance and the 

 course they take in windy weather. The two keys split 



Fig. 23. Oak. A, entire acorn ; 

 B, C, embryo with cotyledons 

 split apart; D, embryo cut 

 across ; E, P, stages in ger- 

 mination. 



