MICROSCOPIC FORMS OF VEGETABLE LIFE. 



259 



1.52. 



water they lose all form, and appear like pieces of jelly, without trace of 

 organization; on immersion, however, the branches quickly resume their 

 former disposition." Their color is for the most part of a brownish- 

 green; but sometimes they are of a reddish or bluish purple. The central 

 axis of each plant is originally composed of a single file of large cylindri- 

 cal cells laid end to end; but this is subsequently invested by other cells, 

 in the manner to be presently described. It bears, at pretty regular in- 

 tervals, whorls of short radiating branches, each of them composed of 

 rounded cells, arranged in a bead-like row, and sometimes subdividing 

 again into two, or themselves giving off lateral branches. Each of the 

 primary branches originates in a little protuberance from the primitive 

 cell of the central axis, precisely after the manner of the lateral cells of 

 Conferva glomerata ( 252); as this protuberance increases in size, its 

 cavity is cut off by a septum, so as to render it an independent cell; 

 and by the continual repetition of the process of binary subdivision, this 

 single cell becomes converted into a beaded filament. Certain of these 

 branches, however, instead of radiating from the main axis, grow down- 

 wards upon it, so as to form a closely-fitting investment that seems prop- 

 erly to belong to it. Some of the radiating branches grow out into long 

 transparent points, like those of Chae- 

 tophoraceae; and within those are pro- 

 duced 'antherozoids,' which, though 

 not endowed with the power of spon- 

 taneous movement, find their way to 

 the germ- cells contained in other 

 parts of the filaments; and by the fer- 

 tilization of the contents of these are 

 produced 'oospores/ which are seen as 

 dark bodies lying in the midst of the 

 whorls of branches (Fig. 152). 



258. Among the highest of the 

 Algae in regard to the complexity of 

 their Generative apparatus, which 

 contrasts strongly with the general 

 simplicity of their structure, is the 

 Family of Characem (ranked by some 

 Botanists as a group of primary im- 

 portance); some members of which 

 have received a large amount of atten- 

 tion from Microscopists, on account 

 of the interesting phenomena they exhibit. These humble plants are for 

 the most part inhabitants of fresh waters, and are found rather in such 

 as are still, than in those which are in motion; one species, however, may 

 be met with in ditches whose waters are rendered salt by communication 

 with the sea. They may be easily grown for the purposes of observation 

 in large glass jars exposed to the light; all that is necessary being to pour 

 off the water occasionally from the upper part of the vessel (thus carry- 

 ing away a film that is apt to form on its surface), and to replace this by 

 fresh water. Each plant is composed of an assemblage of long tubiform 

 cells, placed end to end; with a distinct central axis, around which the 

 branches are disposed at intervals with great regularity (Fig. 153, A). In 

 the genus Nitella, the stem and branches are simple cells, which some- 

 times attain the length of several inches; whilst in the true Char a each 

 central tube is surrounded by an envelope of smaller ones, which is 



Batrachospermum moniliforme. 



