24 THE BOOK OF NATURE STUDY 



are contained in receptacles that look like little pills covered with 

 short hairs ; hence the name of the plant. The stem creeps under 

 water, rooting at every node. The leaves are very narrow, 

 and grow upwards ; they are bright green, from one to three 

 inches in length, and rolled inwards at the top, just as the frond 

 of a fern is. 



The Quillwort (Isoetes lacustris) is found in the shallow water 

 by the edges of lakes, as, for instance, near a boathouse. The 

 easiest way of getting it is to go out in a boat a yard or two, to 

 a spot where its dense, dark green tufts can be seen through the 

 water, and then to pull it up from the bed of the lake. The root- 

 stock is very short indeed, and bears tufts of leaves. The spore- 

 cases are enclosed within the base of the leaves, and the spores are 

 of two sizes. These plants with two sets of spores form a link 

 between the Ferns on the one hand and the Flowering Plants on 

 the other. The small spores may be compared with the pollen 

 grains of the flowering plant, and the large spores with the embryo- 

 sac of the ovule. 



The Awlwort (Subularia aquatica) also belongs to the shallow 

 edges of ponds and lakes, more especially to alpine districts. It 

 is found in the mountainous regions of Scotland, North-western 

 England, North Wales, and Western Ireland, but is by no means 

 common. It is usually entirely submerged, and is about two 

 inches high. The leaves are radical, the flowers have minute 

 white petals. The pod is short and broad, and dehisces from the 

 base upwards, as in the Crucifers generally. 



The Naiads the nymphs of waters and springs in classical 

 lore are slender submerged plants with linear leaves often 

 crowded into clusters ; the flowers are small and sessile in their 

 axils. There are three species occasionally found in this country : 

 the Slender Naiad in Perthshire, Skye, and Connemara ; the 

 Holly-Leaved Naiad, found only in Hickling Broad, Norfolk ; and 

 the Grassy Naiad, in Lancashire. This fresh-water genus is not 

 nearly as common as the marine herb, the Grass- Wrack, which 

 belongs to the same order. This latter has a creeping stem, 

 which roots in the sand or mud and is found most abundantly at 

 or below low-water mark. The Hornworts have no roots, the 

 absorption of food taking place entirely from the surface of the 



