THE EMBRYO CONTINUED. 13 



23. We pluck the ripe fruit, — Pea, for example (Fig. 

 6, e), — open the pod, and take out a seed. This seed has 

 two coats ; the inner one, thin and fine, is called the Teg- 

 men (L. covering) ; it is the Secundine of the ovule. The 

 outer coat is the Testa (L. shell) ; this is the primine of 

 the ovule. It is usually harder and thicker than the teg- 

 men, and often variously carved and appendaged, as we 

 shall see in a future lesson. We carefully remove these 

 seed-coats, and we find the ripe embryo (Fig. 7, A, B). 

 We examine its parts. They are : the Radide, or root, r ; 

 the Gaulicle, or lower stem, t ; the Plumule, or upper stem, 

 g; the Cotyledons, ec. The cotyledons get their name from 

 the Greek kotule, a cup, which they often resemble ; being 

 rounded without and hollowed within. The point of junc- 

 tion between the radicle and caulicle is the Collum, or neck 

 (m). This is quite plain in the Acacia (Fig. 7, B, C) ; but 

 in many plants it is invisible. 



24. Number of Cotyledons. — In Gymnosperms the em- 

 bryo has two, or oftener many cotyledons ; in Angios|)erms 

 there are two divisions : (1) the Grasses, Lilies, Palms, etc., 

 which have but one cotyledon, and which are called Mono- 

 cotyledons ; and (2) the Oak, Apple, Pea, etc., which have 

 two cotyledons and are called Dicotyledons. In mono- 

 cotyledons the cotyledon is sheathing, like a cylinder around 

 the plumule ; and it never leaves the seed nor ascends above 

 ground in germination. In dicotyledons and gymnosperms 

 the cotyledons often ascend, as in the Pea and Maple (Fig. 

 7). The cotyledons are transformed leaves; they are 

 usually called Seed-leaves, because they nourish the young 

 seed in germination, gradually yielding up their store as 

 the plant grows, and then withering. 



25. Germination. — We plant the seed. If it be a mono- 

 cotyledon (Fig. 6, C, D), its plumule alone ascends above 

 ground, and becomes a Caulis, or upper stem, whilst the 

 radicle descends in the ground, and soon perishes; but 

 other roots rapidly spring around the collum, or neck ; and 

 thus we see many fibrous roots in monocotyledons, but no 

 central or tap-root. If the seed be a dicotyledon or a gym- 

 nosperm, its radicle becomes a strong tap-root, as in the 

 Pine, Acacia, and Maple (Fig. 7, C, D), with many 



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