682 MICKOSCOPIC STRUCTURE OF HIGHER CRYPTOGAMS 



growth, with a creeping stein usually branching dichotomously, and 

 imbricated leaves ; but is distinguished from the true mosses, not 

 only by its higher general organisation (which is on a level with that 

 of ferns), but by the character of its fructification, which is a club- 

 shaped * spike,' bearing small imbricated leaves, in the axils of which 

 lie the sporanges. The spores developed within these are remarkable 

 for the large quantity of oily matter they contain, giving them an 

 inflammability that causes their being used in theatres to produce 

 ' artificial lightning.' But in the allied groups of SelagineUece, and 

 Isoetece there are (as in the Rhizocarpece) two kinds of spore pro- 

 duced in separate sporanges ; one set producing ' megaspores,' from 

 which archegone-bearing prothallia are developed, and the other 

 producing ' microspores,' which, by repeated subdivision, give origin 

 to antherozoids without the formation of prothallia. It is a very 

 interesting indication of a tendency towards the phanerogamic type 

 of sexual generation, that the prothallium in this group is chiefly 

 developed ivithin the sporange, forming a kind of ' endosperm,' only 

 the small part which projects from the ruptured apex of the spore 

 producing one or more archegones. The arborescent Lepidodendra 

 and SigiUarice of the Coal-measures seem to have formed connecting 

 links between the Vascular Cryptogams and the Phanerogams, alike 

 in the structure of their stems and in their fructification. For the 

 Lepidostrobi or cone-like * fruit ' of these trees represent the clul >- 

 shaped spikes of the Lycopodiacece ; and seem to have borne ' mega- 

 spores ' in the sporanges of their basal portion, and ' microspores ' 

 in those of their upper part. Some of the best seams of coal appear 

 to have been chiefly formed by the accumulation of these ' mega- 

 spores.' 



Thus, in our ascent from the lower to the higher Cryptogams, we 

 have seen a gradual change in the general plan of structure, bring- 

 ing their superior types into a close approximation to the flowering 

 plant, which is undoubtedly the highest form of vegetation. But 

 we have everywhere encountered a mode of generation which, 

 whilst essentially the same throughout the series, is no less essen- 

 tially distinct from that of the Phanerogam, the fertilising material 

 of the ' sperm-cells ' being embodied, as it were, in self-moving fila- 

 ments, the antherozoids, which find their way to the ' germ-cells ' by 

 their own independent movements, and the ' embryo-cell ' being 

 destitute of that store of prepared nutriment which surrounds it in 

 the true seed, and supplies the material for its early development. 

 In the lower Cryptogams we have seen that the fertilised ob'spore 

 is thrown at once upon the world, so to speak, to get its own living ; 

 but in ferns and their allies the ' embryo-cell ' is nurtured for a 

 while by the prothallium of the parent plant. While the true 

 reproduction of the species is effected by the proper generative act, 

 the multiplication of the individual is accomplished by the production 

 and dispersion of ' gonidial ' spores ; and this production, as we have 

 seen, takes place at very different periods of existence in the several 



