78 CHARACEJE. 



Chara, which are all branched, consist of elongated cells 

 placed end to end, and tapering in size from below up- 

 wards ; surrounding these primary cells there are, in the per- 

 fect state of the plant, a number, in Chara vulgaris usually 

 eighteen, of smaller secondary cells : these take a spiral course 

 round the larger cell invariably from left to right. From 

 the upper extremity of each cell grow out nine arms or 

 smaller cells arranged in a campanulate manner; each of 

 these arms have four or five joints, from which issue the 

 organs of reproduction, to be described hereafter. From the 

 superior extremity of many of the cells also grow out branches, 

 and at the same time long and colourless branched articulated 

 roots are sent forth. The genus Nitella differs only from 

 Chara in the absence of the secondary spiral cells, and in 

 the number of arms which go to form each verticillum or 

 whorl. 



The circulation in Chara was first noticed by Amici ; in 

 the two genera it does not differ materially, in both the course 

 is spiral ; the fluid, with its granules, passing obliquely and 

 slowly from left to right up one side of the cell, turning 

 round its extremity and descending in the same manner on the 

 other side. A circulation of the same character prevails not 

 only in the main cells of the stems and branches, but also in the 

 secondary spiral cells or tubes, some of which are occasionally 

 articulated or divided into other small cells, each, in like 

 manner, having an independent circulation. 



Mr. Slack (Transactions Soc. of Arts, &c., vol. xlix. p. 1.) 

 long since observed, and the observation has been verified, 

 that the ascending current of the circulating fluid is always 

 in that half of each cell which is farthest from the axis of 

 the plant ; the descending, as a consequence, being confined 

 to the opposite half, or that which is nearest the axis. The 

 same observation Mr. Varley states to hold good in respect 

 to the roots, due allowance being made for the difference in 

 their direction, they, unlike the plant itself, taking a down- 

 ward course. 



A deviation from the above-described circulation has been 

 noticed to occur in certain parts of Chara vulgaris by Mr. 



