164 FOOTNOTES FROM 



which every visitor to the sea-coast is familiar, adding 

 greatly to the beauty of rocky pools, left full by the 

 receding tide, also occurs not unfrequently in fresh- 

 water ponds and stagnant waters in spring and summer. 

 An allied species, Tetraspora lubrica, forming irregular 

 masses of considerable extent, and exceedingly lubricous, 

 in gently running water, has its fruit, consisting of 

 minute granules imbedded in the fronds, loosely arranged 

 in fours. The first stages of all these fresh-water repre- 

 sentatives of the marine ulvae, are in all respects simple 

 confervse ; but the cells at the extremity of the filaments 

 divide, and by repeated division, these filaments are 

 laterally expanded, until they form a plaWleaf-like 

 frond, as in ulva, or close all round after they have ex- 

 panded, until they produce a tube or sac as in entero- 

 morpha. 



One of the most singular of the confervaceous algae is 

 the Botrydium granulatum. It grows on the ground in 

 moist shady situations in spring and autumn, and is per- 

 haps more frequent than is supposed, its minute size 

 causing it to be overlooked. It consists of a number of 

 green vesicles of the size of mustard-seed, aggregated 

 together, and sunk, as it were, into the soil, the whole 

 bearing a close resemblance to a miniature branch of un- 

 ripe grapes, whence the name. Under the microscope, 

 each vesicle appears rilled with a watery fluid containing 

 minute granules, which escape when ripe by an opening 

 at the top ; in dry weather the upper part collapses, 

 sinks in, and becomes cup-shaped. The vesicles are 

 attached to the soil by a tuft of root-like fibres, into 

 which their fluid contents descend when pressed. This 



