338 FAMILY CHA.RACE.E '. CYCLOSIS. 



spores ' are formed, by the agglomeration of which are produced the 

 large dark bodies that are seen in the midst of the whorls of 

 branches (Fig. 157). 



254. This seems the most appropriate place to consider a group 

 of humble Plants having a peculiar interest for Microscopists — 

 that, namely, of Characece, — in which we have a Vegetative appara- 

 tus as simple as that of the Protophytes already described, whilst 

 their Generative apparatus is even more highly developed than that 

 of the proper Algae. They 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 carrying away a film that is apt to form on its surface), and 

 to replace this by fresh water. Each plant is composed of an as- 

 semblage 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. 158, a). In one of the Grenera, Nitella, 

 the stem and branches are simple cells, which sometimes attain the 

 length of several inches ; whilst in the true Chara each central tube 

 is surrounded by an envelope of smaller ones, which is formed as in 

 Batrachospermeag, save that the investing cells grow upwards as 

 well as downwards from each joint, and meet each other on the stem 

 half-way between the joints. Some species have the power of se- 

 creting carbonate of lime from the water in which they grow, if this 

 be at all impregnated with Calcareous matter ; and by the deposi- 

 tion of it beneath their teguments they have gained their popular 

 name of ' Stone-worts.' These humble Plants have attracted much 

 attention, in consequence of the facility with which the Cyclosis, 

 or movement of fluid in the interior of the individual Cells, may 

 be seen in them. Each cell, in the healthy state, is lined by a 

 layer of green oval granules, which cover every part, except two 

 longitudinal lines that remain nearly colourless (Fig. 158, b) ; and 

 a constant stream of semi-fluid matter containing numerous jelly- 

 like globules is seen to flow over this green layer, the current passing 

 up one side, changing its direction at the extremity, and flowing 

 down the other side, the ascending and descending spaces being 

 bounded by the transparent lines just mentioned. That the currents 

 are in some way directed by the layer of granules, appear sfrom the 

 fact noticed by Mr. Varley,* that if accident damages or removes 

 them near the boundary between the ascending and descending cur- 

 rents, a portion of the fluid of the two currents will intermingle by 

 passing the boundary ; whilst, if the injury be repaired by the 

 development of new granules on the part from which they had been 



* " Transactions of the Microscopical Society" (First Series), Vol. ii. 

 p. 99. 



