ISOETES. 207 



their basal parts and the decaying remains of the older 

 leaves continuing to encircle the base of the young vigorous 

 leaves springing from the centre. 



The fructification is contained within the dilated bases of 

 the leaves, and consists of roundish, hard, membranous spore- 

 cases. Some of these spore-cases contain roundish bodies 

 or spores, marked with a triangular suture on the top, and 

 a transverse annular one in addition ; these spores separate 

 at the sutures into three triangular valves, exposing an 

 interior subglobose semi-gelatinous substance; externally 

 they are opake, whitish, and rough with minute prominent 

 points. The other set of spore-cases usually said to occur 

 at the base of the inner leaves, while the former occupy the 

 bases of the outer ones, but, according to Mr. Newman, not 

 following any law in their relative position contain minute 

 angular sporules, which are very numerous, and of a pale 

 yellow colour. These different kinds of spores have been 

 sometimes called anthers and ovules, as have the similar 

 bodies in the Club-mosses ; but it is rather to be considered 

 that the smaller grains are the imperfect representatives of 

 the larger ones, since as yet we possess no good evidence of 

 the sexuality of this race of plants. 



Two distinct-looking forms of the Quillwort have been 



