786 LIFE : OUTLINES OF GENERAL BIOLOGY 



naturalist, gardener or even florist to this day: and since for adequate 

 understanding of this matter a laboratory course is necessary, no 

 popularisation of this subject is adequately possible, and we can here 

 only give the barest outline of the main result. Linnaeus, in estabhsh- 

 ing for the flowering plants the name of Phanerogamia (evident sexes), 

 expressed this everyday view; yet his reflective intuition cLs to 

 the apparently flowerless plants — ferns, mosses, equisetums, lyco- 

 pods, with algae, fungi, etc. — is manifest in his general name for 

 them as Cryptogamia, which expressed his anticipation that sex 

 was here but hidden, as was in time confirmed. But it was not until 

 the middle of the last century that Hofmeister revolutionised the 

 whole subject, by producing convincing evidence that the so-called 

 Cryptogams plainly and unmistakably exhibited the sexual process 

 of reproduction, and this usually in "alternate generations" with the 

 asexual, as so well demonstrated in the fern. For that familiar type, 

 with its spore-bearing leaves, is but the asexual generation. The 

 sexual generation is the tiny prothallus, at first naturally mistaken 

 for a difterent kind of plant altogether — a mere liverwort. It is this 

 which arises from the spore. Its small ova are each contained in a 

 flask-like "archegonium", while the male elements are set free from 

 equally distinctive "antheridia". It is the fertilised ovum which 

 develops into the fern anew. The reciprocal case occurs in mosses; 

 for the spore-bearing generation is here reduced to the moss-capsule 

 and its stalk, while the leafy-looking moss body is the sex-bearing 

 generation, in this case the actively vegetative one. This, however, 

 is exceptional, as from the ordinary contrast of vegetative growth 

 and reproductive cost we might expect. Hofmeister's study of the 

 Lycopods was also very helpful: since in these the spores are of 

 two kinds, large and small, megaspores and microspores, the former 

 producing the larger prothalli of the more growing female sex, 

 with their characteristic archegonia, and the smaller spore the small 

 male prothallus, producing fertilising elements. 



Passing to the flowering plant, Hofmeister's keen re-examination of 

 the embryo-sac (which after fertilisation produces the plant embryo, 

 long before vaguely known within the ovule), revealed this as a 

 macrospore corresponding to that of the Lycopod. And within this 

 he identified not only the ovum, but the minute homologue of the 

 prothallus; which develops at last into what earlier botanists had 

 called the albumen, and later ones the endosperm. But this attractive 

 identification seemed at first but dubious, for where was the arche- 

 gonium so characteristic of the higher cryptogams? Here the 

 difficulty was substantially overcome through the examination of 

 the ovules of conifers, which revealed the embryo-sac as megaspore, 

 with ample prothallus, and unmistakable archegonia, though 

 reduced. So next returning to the embryo-sac of the flowering plant, 

 the last vestiges of the archegonium were then reasonably identified. 



