142 



3. Club-mosses. Plants with numerous small scattered 

 leaves. Sporophylls resemble foliage leaves but are 

 sometimes aggregated into conelike flowers. 

 Sporangia are borne singly either on the upper 

 surface of the sporophyll, or on the stem. 



Now, in the true ferns, the asexual spores are all alike and 

 one and the same prothallium bears both antheridia and 

 archegonia. In some Pteridophytes, however, the spores 

 are of two kinds, the larger ones being termed macrospores 

 and the smaller ones microspores. These are contained in 

 separate sporangia which are called, respectively, macrospor- 

 angia and microsporangia ; the leaves bearing the former 

 being the female sporophylls and the leaves bearing the latter 

 the male sporophylls. From the macrospore is developed a 

 female prothallium which produces only archegonia and 

 from the microspore a male prothallium producing only antheri- 

 dia. Moreover, in such plants, the prothallium is in every 

 case pulled further back into the spore, from which it now 

 never becomes independent, as we have seen to be the case 

 in the ferns. The male prothallium in particular becomes 

 very much reduced and consists of only a few cells. Moreover, 

 in the Horsetails and some Club mosses the sporophylls are 

 aggregated into small, cone-like flowers. These plants thus 

 lead us up to the great group of the most highly developed 

 plants, known as the : 



125. Phanerogams. This contains 



all the plants which are not included in the groups already 

 enumerated and briefly described above, and hence it 

 includes practically all our forest trees and shrubs. These 

 plants exhibit a distinct differentiation into true root, stem 

 and leaves, and possess true vascular bundles. They are 

 characterised by the production of true seeds., and the 

 majority possess flowers containing structures which we at 

 once recognise as stamens and carpels. In Phanerogams, 

 as in the higher Cryptogams, there is an alternation of 

 generations, although at first sight this is not obvious, 

 owing to the great reduction in the oophyte, that which 

 we see and recognise as the ' ' plant ' : being the sporo- 

 phyte. The various organs and members of phanerogamic 

 plants were described and received definite names when the 

 life histories of most of the cryptogams were very imperfectly 

 known. This led to different names being given to organs 

 which are really homologous and this has resulted in further 

 obscuring the resemblances between the plants of these two 



