ON BIOLOGICAL ANALOGIES. 271 



without sexual fertilization. These spores germinate and produce 

 a little plant called a prothallium, not at all like the parent fern, 

 but a small simple plant nourished by root- hairs. This prothal- 

 lium is capable of repeating itself by buds, but finally it produces 

 male and female organs, and the result of fertilization is a true 

 embryo, sexually produced, which develops into a Fern, like its 

 asexual parent. Thus there is an alternate asexual and sexual 

 generation, the sexual being the small prothallium, and the asexual 

 that more imposing form which we are in the habit of calling a 

 Fern. 



In Mosses a somewhat similar alternation prevails. The germina- 

 ting spore produces a confervoid thallus called a Protonema, from 

 this the leafy moss is developed by buds on the branches. Sexual 

 organs are formed, and finally, after fertilization, spores are produced. 



It is unnecessary to repeat instances, since my object is more sug- 

 gestive than exhaustive, and in fact the subject could not possibly 

 be extended in all its details within the narrow limit of time at my 

 disposal. Fanciful analogies have been propounded by some 

 botanists, to which allusion is made in Sachs' " Text Book " (p. 

 228) ; but it is unnecessary to refer to them further. Some also 

 claim for the sEcidiomycetes a true alternation of generations, but 

 the continuity is not sufficiently established, with alternate reversion 

 to an embryonic condition, to warrant acceptance as a morphological 

 fact.* 



" Parthenogenesis is the term used to express the fact that plants 

 (or animals) which possess normal male organs of fertilization, and 

 in which embryos are developed by the fertilzation of the oospheres 

 may occasionally develop embryos from female cells which have not 

 been fertilized, but which are nevertheless capable of complete 

 development." f This is not an uncommon phenomenon in the 

 animal kingdom, but is comparatively rare in plants. It was sup- 

 posed at one time that Ccelebogyne ilicifolia \ presented a clear case 

 of parthenogenesis, but recent researches have thrown doubt upon it, 

 inasmuch as the phenomena seem rather to be attributable to a kind 



* Leuckart, who began by separating parthenogenesis from alternate 

 generation, saw an essential difference between the two phenomena, viz., 

 that in the first fecundation may occur before every reproductive act, but 

 that in the second it must occur from time to time in certain fixed acts of 

 reproduction. " Biblioth. Univ. de Geneve," 1859. 



t Sachs' " Text Book of Botany," Ed. ii., p. 902. 



X J. Smith, " Linnean Transactions," xviii., p. 503. 



Journ. Q. M. C, Series II., No. 6. y 



