GRAMINE^R. 



1019 



I. QUILIiWORT. ISOETES. 



• 

 Stock very short, rooting at the base, bearing a tuft of linear leaves, 

 the whole plant usually under water. Capsules more or less enclosed 

 within the enlarged base of the leaves, those of the outer leaves filled 

 with minute powdery granules, those of the inner leaves containing 

 larger grains, at first cohering in fours. 



A small genus, widely spread over the greater part of the globe. 



1. European Quillwort. Isoetes 

 lacustris, Linn. 



(Fig. 1240.) 

 (Eng. Bot. t. 1084.) 



A perennial, of a bright green, forming 

 dense tufts under the water. Leaves 

 narrow-linear, much like those of several 

 Monocotyledons, varying from 2 to 6 

 inches long, their enlarged bases giving 

 the plant often a bulbous appearance. 



In mountain pools, and shallow lakes, 

 in central and northern Europe, northern 

 and Arctic Asia, and JN"orth America. In 

 Britain, in the mountainous parts of 

 Scotland, northern England, Wales, and 

 Ireland. Ft. summer and autumn. Mo- 

 dern botanists distinguish as a species 

 under the name of I. echinospora, a form 

 found in our mountain lakes, often grow- 

 ing with the common one, but said to be 

 only where the soil is peaty. It differs 

 chiefly in the larger spores covered with 

 acute tubercles instead of being granu- 

 late only or nearly smooth on the surface. 

 A rather more distinct-looking form re- 

 ferred by Hooker to I. Du-ricei (Fig. 

 1241) and by Babington to I. hystrix, 

 occurs in moist sandy hollows on Lan- 

 cresse Common in Guernsey. The root- 

 stock is covered outside the tuft of leaves 

 with a number of small imbricate toothed 

 or jagged brown scales, which are the 

 persistent remains of old leaves, and 

 which are never observed in the common 

 under-water forms. It remains to be 

 seen how far this difference may be owing 

 to situation. 



