M'Nab — Remarks on Stages of Vegetable Metagenesis. 463 



It will further be seen that for the non- sexual stage we have 

 now in use a set of terms — spore, sporangium, sporophore — terms 

 universally accepted, and the words gamete, gametangium, game- 

 tophore, would, if adopted, at once indicate a similar series of re- 

 lationships in the sexual stage of development. 



But we can advance one step further, and distinguish between 

 reproduction by spores and reproduction by buds, and attempt to 

 solve that most difficult botanical question, as to what is a spore. 

 It is quite obvious that the spore must be associated with a spore- 

 case or sporangium, and in all instances in which several spores 

 originate in a spore-case no difficulty can arise, and there can be 

 no such things as endoconidia. It is, however, quite different 

 when only one spore is produced in a spore- case; but here we in- 

 variably find that the spore either develops a special wall inside 

 the wall of the sporangium, or else the spore escapes as a naked 

 mass of protoplasm, and only develops a wall at a later stage. 

 Now, if we apply this character to many of the reproductive bodies 

 of the lower plants, we find that the different forms of conidia are 

 all single detachable cells, without that inner wall which would 

 indicate the formation of a spore inside a sporangium. Conidia 

 are thus buds which become detached from the parent plant. 

 Usually among the Fungi both spores and conidia are formed, 

 there being often several kinds of conidia developed by one plant. 

 As gamogenesis is exceedingly rare in Fungi, the reproduction is 

 either by spores or conidia, or by both, as in most of the Ascomy- 

 cetes. A question will arise as to the so-called spores of the Basi- 

 diomycetes. As they arise like conidia,^ and produce no special 

 internal wall inside the special swelling of the end of the sterig- 

 mata of the basidium, I believe we must regard them as a group 

 of Fungi which have lost the power of producing spores and only 

 multiply by conidia. This is the last step in development in the 

 Fungi, as it is only in the lower forms that sexual reproduction 

 exists, and even in them apogamy or parthenogenesis becomes 

 marked. Thus true alternation of generations ceases and we have 

 multiplication by spores or by conidia, the conidia alone remaining 

 (Basidiomycetes) ; or the spores are only produced under excep- 

 tional conditions, as in Penicillium and other Ascomycetes. 



1 See Vines. Prantl's Text-Book of Botany, p. 141. 



SCIEN. PKOC. R.D.S. VOL. IV. PT. VIII. 2 Q 



