Biological Papers. 277 



Order VII. HYDROPTERIDALES. The Water Ferns. 



Family 21. Salviniace^. Floating-fern family. 



Azolla. 

 Family 22. Marsileace^. Water- fern family. 

 Marsilea. 

 Order VIII. ISOETALES. The Quillworts. 



Family 23. ISOETACE^. Quillwort family. 



SuBPHYLUM B. ARTHROCAULOiNES. Joint-stemmed Pteridophytes. 

 Class IV. Equisetine^. Joint-rushes. 



Order IX. EQUISETALES. The Horsetails. 



Family 24. Equisetace^. Horsetail family. 

 Equisetum. 



SuBPHYLUM C. LEPIDOCAULONES. Scaly-stemmed Pteridophytes. 

 Class V. Lycopodine^. Club-mosses. 



Order X. SELAGINELLALES. The Little Club-mosses. 



Family 25. SelaginellacejE. Ground-fir family. 

 Selaginella. 



Subkingdom II. ARCHEGONIATA. 



Archegoniate Spore-Bearing Plants. 



Aerial, terrestrial, moisture-loving, chlorophyl-developing plants, gen- 

 erally small, with a well-defined "alternation of generations," being in 

 reality the different stages or phases of a cycle of life. 



One is an oophoral, or ovum-bearing, stage, called gametophyte. This is 

 the final stage in the life cycle of a plant; though in the archegoniates it 

 appears to be the first. In this stage the plants, entirely cellular and with 

 or without chlorophyl, so differ that some of the plants, when dioecious, 

 bear antheridia, or antheridial sacs, which carry till they ripen many an- 

 theridial bodies called antherozo'ids or spermatozo'ids, minute specialized 

 bodies, endowed with the power of voluntary motion under water, that take 

 part in the reproduction of their own species under certain fixed conditions; 

 others of the plants bear what are called archegonia, sacs containing a 

 single ooidal cell or oosphere, which, on being impregnated by fusion with 

 it of an antherozoid from an antheridial plant, clothes itself with a cell wall 

 and becomes an oospore. When monoecious, both kinds of reproductive 

 bodies are borne on the same plant; and the process gone through with is 

 precisely the same. The derived oospore is either a fertile thin- walled cell 

 ready to germinate at once, or is a thick-walled cell analogous to a seed 

 and must pass through a formative period of rest before germinating; then, 

 conditions being favorable, may develop into a liverwort, a moss, a fern, or 

 a horsetail, exactly as the parent plants were. The process is called 

 oogamy; the minute functional bodies are called gametes. 



The other is a sporophoral, or spore-bearing, stage, called sporophyte. 

 It is a direct product of the oospore; and is a plant in which reproductive 

 bodies are not developed, but which is capable for a time of multiplying 

 vegetatively, and finally of bearing nonsexual spores in uncountable num- 

 bers, any of which, falling in a suitable place, and conditions being favor- 

 able, may develop into and produce the oophores, or gametophytes, as 

 before. 



This is the natural process of all creation. "The child is father to the 

 man" is a very old and well-established saying. The man, we know, is fa- 



