1524 



CHAPTER LXVII. 



SUB-KINGDOM C R M O P H Y T A— continued. 



Series Phanerogams. — Class Gymnosperms. 



Series III. Phanerogams. — The Phanerogams, which include 

 the whole of the remaining groups of plants, are characterised by 

 the production of a seed, and the consequent concealment or com- 

 pression of the alternation of generations. It has already been 

 mentioned that in several groups of Pteridophytes the tendency of 

 the oophore (prothallium) is to lose its independent existence, but 

 in the present series this independence is totally suppressed. Thus 

 the macrospore or female element, now termed the embryo-sac, is 

 never detached from the main plant, or sporophore, previous to 

 fertilisation ; while the oophore, now known as the endos_pe?-m, which 

 may be rudimentary, is always enclosed in the macrospore (embryo- 

 sac). The seed is developed from the ovule (of which the envelope 

 is known as the testa), which produces the embryo-sac, and in this 

 the endosperm and the oosphere. The latter is fertilised by the 

 pollen-tube or outgrowth from the pollen-g?-ain, which represents the 

 microspore of the Pteridophytes. 1 The plant is always differentiated 

 into stem, leaves, roots, and hairs ; and its branching is normally 

 monopodial, the main axis continuing to grow and producing its 

 lateral shoots and roots beneath its apex. Phanerogams are further 

 characterised by the metamorphosis and differentiation of homo- 



1 It is thus evident that the Phanerogam with its pollen-grains and embryo-sacs 

 is equivalent to the sporophere of the Pteridophytes. The sexual differentiation, 

 which in the most specialised members of the latter commences with the formation 

 of macrospores and microspores, is, however, carried further back, being mani- 

 fested not only in the formation of embryo-sac and pollen-grains, but also in the 

 differences between ovule and pollen-sac, and between the modified leaves {carpels 

 and stamens) bearing them, and, even earlier, in the distinction between male 

 and female flowers, and finally in the development of separate male and female 

 {dioecious') plants. At least for a time, the seed unites in itself the two genera- 

 tions — the prothallium (endosperm), and the embryo or young plant of the second 

 generation. (Sachs.) 



