STRUCTURAL BOTANY. 65 



The growth of the plantlet, after it springs from the 

 seed, is simply a continuation of the same process of cell- 

 division. But the plantlet, or embryo, must have grown 

 and developed first in the seed, ere it can separate from it. 



Of the seed we shall treat below, when we come to the 

 fruit. Still we may at once state, that the ovule, after fer- 

 tilization, or after the embryo is formed, is called seed. 



II. Peotecting Organs of the Flowek. 



116, The Pkotecting Oegans of the flower are the 

 floral leaves, called the perianth, wliich supports and pro- 

 tects the stamens and pistils. The perianth is, as was 

 stated in § 34, either double or simple. But the term 

 perianth is often used instead of the phrase simple peri- 

 anth, for brevity's sake, or whenever we can not readily 

 distinguish which leaves compose the calyx, and which the 

 corolla. 



117, The leaves of the perianth we consider to be mo- 

 dified ordinary leaves. In very many instances we find a 

 gradual transition from ordinary leaves into sepals, and 

 from sepals into petals ; and the latter, when present in 

 great number, gi'ow smaller by degrees toward the axis of 

 the flower, and are often stamen-like. Stamen-like petals 

 we call staminodia, as in Nymphsea. 



118, The Calyx, considered with respect to its form 

 and duration, is simple, when consisting of one set of 

 sepals only ; double, when surrounded by an involucel (a 

 whorl of bractlets), as in certain Mallows (we then have an 

 involucellate calyx, in contradistinction to a naked calyx) ; 

 PERSISTENT, not falling away after flowering, sometimes 

 enlarging in fruit, as in Physalis, or becoming fleshy, as in 

 the Eose ; deciduous, falling away before flowering, as in 

 the Poppy, or immediately after floration, as in the Cherry ; 



