GERMINATION OF FERN SPORES. 2$ 



A. Production of the spores asexually by the mature plant. 



(FRUCTIFICATION.) 



B. Growth of the prothallium from the spore with or with- 

 out the development of a pro-embryo. (THALLOID PHASE.)* 



C. Production of sexual organs, archegonia (female) and 

 antheridia (male), on the under surface of the prothallium, or 

 on separate prothallia. 



D. Fecundation of the oosphere developed in the arche- 

 gonium by the antherozoids developed in the antheridium. 



(FERTILIZATION.) 



E. Growth of the mature fern in successive stages from 

 the oospore. (PTERIDOID PHASE.)* 



LITERATURE.t 



BESSEY (Charles E.). Botany, pp. 361-388. New York, 

 1881. (Henry Holt & Co.) 



GOEBEL (K.). Outlines of Classification and Special Mor- 

 phology of Plants, pp. 189-298. (English Translation.) Ox- 

 ford, 1887. (Macmillan & Co.) 



CAMPBELL (Douglas H.). Fern Notes. In Torrey Bulletin, 

 x, 1 1 8, 119. (Nov. 1883.) 



The Development of the Prothallia in Ferns. In Botan- 

 ical Gazette, x, 355-360, with Plate IX. (Oct. 1885.) 



* The terms " Thalloid Phase" and " Pteridoid Phase" in place of the 

 older terms " sexual generation" and "asexual generation" were first sug- 

 gested in the first edition of this work (1881). The older terms, although in 

 common use by botanical writers, are decidedly unfortunate and misleading. 

 A generation is properly the production of offspring resembling the parent, 

 or the offspring thus produced, which the prothallium is not and the mature 

 fern is not. The generation proper must then be considered as including the 

 entire life-history of a fern, of which the prothallium and mature fern are suc- 

 cessive phases. The terms "sexual " and "asexual " as used in this connec- 

 tion are likewise misleading, as they might apply as well to the origin as to 

 the producing power of the so-called " generation." The prothallium is asex- 

 ual in origin, but develops sexual organs ; the mature fern, on the other hand, 

 produces no sexual organs, but is itself the product of bisexuality. The same 

 criticism applies with equal force to the expression " alternation of genera- 

 tions," used alike by botanists and zoologists. 



t As elsewhere, reference is made mainly to American literature. The 

 more extensive European literature is already well catalogued in Goebel's 

 Outlines, so is not repeated here. 



