350 THE MICROSCOPE AND ITS REVELATIONS. 



have alighted on a damp surface. If a number of these spores be spread 

 out on a slip of glass under the field of view, and, whilst the observer 

 watches them, a bystander breathes gently upon the glass, all the fila- 

 ments will be instantaneously put in motion, thus presenting an extremely 

 curious spectacle; and will almost as suddenly return to their previous 

 condition when the effect of the moisture has passed off. If one of the 

 tliecce which has opened, but has not discharged its spores, be mounted in 

 a cell with a movable cover, this curious action may be exhibited over and 

 over again. These spores, like those of Ferns, evolve themselves into a 

 prothallium; and this develops antheridia, and archegonia, the former at 

 the extremities of the lobes, and the latter in the angles between them. 



346. Nearly allied to Ferns, also, is a curious little group of small 

 aquatic plants, the Rhizocarpece (or pepper- worts), which either float on 

 the surface, or creep along shallow bottoms. These all agree in having 

 two kinds of spores, produced in separate capsules; the larger, or ' mega- 

 spores,' giving origin to prothallia which produce archegonia only; and 

 the smaller, or ' rnicrospores/ undergoing progressive subdivision, usually 

 without the formation of a distinct prothallium, each of the cells thus 

 formed giving origin to an antherozoid. In this, as we shall presently 

 see ( 349), there is a distinct foreshadowing of the mode in which the 

 generative process is performed in Flowering Plants; the 'microspore' 

 obviously corresponding to the pollen-grain, while the 'megaspore 7 may 

 be considered to represent the primitive cell of the ovule. 



347. Another alliance of Ferns is to the Lycopodiacece (Club-mosses); 

 a group which at the present time attains a great development in warm 

 climates, and which, it would seem, constituted a large part of the 

 arborescent vegetation of the Carboniferous epoch. In the Lycopodiew 

 proper, the sporangia are all of one kind, and all the spores are of the 

 same size; each, as in Opliioglossum ( 343), giving origin to a subterran- 

 eous prothallium, that develops both antheridia and archegonia. The 

 plant which originates from the fertilized ' germ-cell ' of the archegonium, 

 only attains in colder climates a Moss-like growth, with a creeping stem 

 usually branching dichotomously, and imbricated leaves; but is distin- 

 guished from the true mosses, not only by its higher general organization, 

 (which is on a level with that of Ferns), but by the character of its fructi- 

 fication, which is a club-shaped 'spike/ bearing small imbricated leaves, 

 in the axils of which lie the sporangia. The spores developed within 

 these are remarkable for the large quantity of resinous matter they con- 

 tain, giving them an inflammability that causes their being used in 

 theatres to produce 'artificial lightning.' But in the allied groups of 

 Selaginellece and Isoetecv, there are (as in the Rlnzocarpece) two kinds of 

 spores produced in separate sporangia; one set producing ' megaspores,' 

 from which archegonia-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 gene- 

 ration, that the prothallium in this group is chiefly developed within the 

 spore-case, forming a kind of ' endosperm ' ( 349), only the small part 

 which projects from the ruptured apex of the spore producing one or 

 more archegonia. The arborescent Lepidodendra and SigillaricB of the 

 Coal-measures seem to have formed connecting links between the Vascu- 

 lar Crytogams 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 



