100 THE MORPHOLOGY 



of gradations is exhibited by them in the formation of 

 the reproductive cells, which, in the Liver-worts and 

 Mosses are found in a morphologically indefinite capsule, 

 in the succeeding groups come into more intimate con- 

 nection with the leaf, and at last assert so strongly their 

 exclusive claim ta definite foliaceous organs, that the said 

 organs lose all their resemblance to the other leaves. As 

 the reproductive cells are called spores, these leaves receive 

 the name of "spore-leaves" and in the Horsetails they 

 have the same form as in the succeeding and highest of 

 the great divisions of the stem-plants, which form, in the 

 sexual or Phanerogamous plants, is that of stamens with 

 their anthers. 



In the Liver-worts, Mosses, and Ferns, we find an. 

 organ of a peculiar kind, which in its structure corresponds 

 to the seed-buds of the sexual plants ; its morphological 

 import is as yet undetermined, its physiological relations 

 are wholly inexplicable at present, but it certainly has no 

 essential connection with the reproductive functions. These 

 organs are usually called antheridia. They remind us 

 very strongly of a phenomenon observed in the progressive 

 gradations of animals, where we also often find an organ 

 prefigured in a group or genus in which it performs no 

 function, acquiring its actual importance to the life of the 

 animal in a neighbouring group. 



Stem and leaf as elementary organs, definite leaves 

 transformed into spore-leaves for the formation of repro- 

 ductive cells, and an organ of an uncertain nature with the 

 structure of a seed-bud, these are the acquisitions with 

 which Nature enters upon the development of the last 

 great division of the Vegetable Kingdom, the group of 

 Sexual Plants. The characteristic of this group is the 

 entrance of the seecUbud upon its true office, that of a 



