32 BOTANY 



capsules of striking form, which are usually alike, but in the more 

 specialized forms show two kinds, one producing large spores which 

 give rise to a female gametophyte, the other to smaller ones, from 

 which grows the minute male gametophyte. The origin of the 

 spores and their essential structure is remarkably uniform through- 

 out the higher plants. 



The sporophylls of the Ferns are sometimes of quite peculiar form, 

 and in the similar Horsetails and Club-mosses are arranged in cones 

 which are comparable to the flowers of the simpler Seed-plants, like 

 the Pines and Firs. 



The sporophylls of the "Flowering Plants" (Spermatophytes, 

 Phanerogams) are always of two kinds, known respectively as Car- 

 pels and Stamens, Upon the former are borne sporangia (ovules), 



which contain the large spores 

 (macrospores), and upon the stamens 

 are the microsporangia, or pollen- 

 sacs, in which the small spores (mi- 

 crospores) are contained. In most 



S K^^^P ;;V ii^^7 Flowering Plants the foliar nature 



of the sporophylls is much less obvi- 

 ous than it is in the Ferns (Fig. 26). 

 FIG. 26. -Section of "the flower of Accessory Floral Leaves. Associ- 

 Ranunculus repens, slightly en- ated with the sporophylls of the 

 larged; s, sepals; p, petals; an, s pe rmatophytes, there are often 

 stamens; ay, carpels. ~, , ,.., , , 



other more or less modified leaves, 



the Sepals and Petals, which, with the sporophylls, make up the 

 Flower (Fig. 26). 



The macrospore in the Spermatophytes never leaves the sporangium 

 (ovule), but germinates and passes through the development of the 

 gametophyte within the ovule. The latter grows with the develop- 

 ing gametophyte within it, and finally drops away and is known as 

 a Seed, which is only a metamorphosed sporangium. The carpels 

 undergo a corresponding growth and produce the " Fruit " of these 

 plants. 



Morphology and Classification 



A comparative study of the structure of plants is the surest clew 

 to their relationships, and must form the basis of every natural 

 classification. All modern systems of classification are based upon 

 the assumption that structural resemblances indicate to some degree, 

 at least, actual genetic relationship. As the life-history of the indi- 

 vidual is supposed to repeat to a certain extent the development of 

 the race, the importance of Ontogeny, or individual development, 

 in determining the Phylogeny, or pedigree, of any group of organ 

 isms, is sufficiently obvious. 



