EQUISETACEA: ; RHIZOCARPE/E ; LYCOPODIACE^: 68 1 



the spore, in the manner represented at A, though more closely 

 applied to the surface ; but, on the liberation of the spore, they ex- 

 tend themselves in the manner shown at B, the slightest application 

 of moisture, however, serving to make them close together (the 

 assistance which they afford in the dispersion of the spores being no 

 longer required) when the spores 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 filaments will be instanta- 

 neously put in motion, thus presenting an extremely curious spec- 

 tacle, and will almost as suddenly return to their previous condition 

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

 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, develop into a 

 prothallium ; and this bears antherids and archegones, the former at 

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

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

 aquatic plants, the Rhizocarpeae (or Pepper- worts), which either 

 float on the surface or creep along shallow bottoms. These differ 



FIG. 523. Spores of Equisetum, with their elaters. 



from Ferns and Horse-tails in having two kinds of spore, produced 

 in separate sporanges ; the larger, or * megaspores,' giving origin to 

 prothallia which produce archegones only; and the smaller, or 

 * microspores,' 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, 

 there is a distinct foreshadowing of the mode in which the genera- 

 tive process is performed in flowering plants, the * microspore ' cor- 

 responding to the pollen-grain, while the ' megaspore ' may be con- 

 sidered to represent the primitive cell of the ovule. 



Another alliance of Ferns is to the Lycopodiacese (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 

 LycopodieoK proper the sporanges are all of one kind, and all the 

 spores are of the same size, each, as in Ophioglossum, giving origin 

 to a subterraneous prothallium that develops both antherids and 

 archegones. The plant which originates from the fertilised ' germ- 

 cell ' of the archegone attains in colder climates only a moss-like 



