682 MICROSCOPIC STRUCTURE OF HIGHER CRYPTOGAMS 



growth, with a creeping stem 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 SelagineUeoe and 

 IsocteiK 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 if it//! it 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 Lfpidode/t^ru 

 and fiigillarifti 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 club- 

 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 ' meya 

 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 1 lie 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 1 rue seed, and supplies the material for its early development . 

 In the lower < Yyptogains we ha\e seen that the fertilised oiispore 

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

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

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

 /I/II-IH! nclinn < if ili,' species is ell'ected 1 iv the proper generative act, 

 the multiplication <>j' lln- individual is accomplished by the production 

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

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



