ALGAE. CHARACEAE. 



53 



The species are many and are found in all parts of the world ; but they agree 

 so closely with one another, that they may be all comprehended in two genera, Chara 

 and Nitella ; these have been recently divided again each into two genera. 



The germinating oospore does not produce a sexual leafy plant at once. At the apex 

 of the oospore a small lenticular cell filled with clear finely granular protoplasm is 

 divided off from a larger one which contains reserve food-material ; the latter is called 

 by De Bary the basal cell, the former the first nodal cell, and from it the further develop- 

 ment of the embryo plant proceeds. The basal cell suffers no further change beyond 

 parting with its food-material ; the first nodal cell, on the other hand, divides by a 

 vertical wall coinciding with the longitudinal axis of the oospore into two daughter-cells, 

 each of which developes into a tube. One of these is the 

 so-called primary or main root (Fig. 29, iv'}, the other the 

 pro-embryo, which consists at first of a simple row of cells 

 with limited apical growth. Two disk-like nodes are then 

 formed in it, a rhizoid-forming-node (Fig. 29, </), and a stem- 

 node (Fig. 29, g). The disk-shaped nodal cell is divided by 

 longitudinal septa into two inner and six to eight peripheral 

 cells. One of the latter, the first formed, is the growing- 

 point of the Chara-plant, the others give rise to a few rudi- 

 mentary leaves. Further details are given below. 



The main shoot which bears the sexual organs has un- 

 limited apical growth. It has an apical cell (Fig. 30, /) 

 from which segments are cut off by transverse walls. Each 

 segment is again divided by a transverse wall into two cells 

 lying one above the other ; the lower of these (g) does not 

 divide again, but becomes an internode, which may be 5-6 

 centimetres long ; the upper, while scarcely elongating at 

 all, divides by a vertical wall into two halves, and in each 

 half a whorl of peripheral cells (b, ft) is formed by further 

 successive (anticlinal) walls. From the node thus formed 

 the leaves are developed, one from each of the peripheral 

 cells, and the normal lateral twigs spring from the axil of 

 the first or the first two leaves of the whorl. The develop- 

 ment of the 4-10 leaves of the whorl repeats the processes 

 of growth in the stem with some modifications ; but their 

 apical growth is limited ; the apical cell ceases to divide 

 after the formation of a definite number of cells, and grows 

 into the usually pointed terminal cell of the leaf (Fig. 30, 

 A, b"}. Lateral leaflets (secondary rays) may spring from 

 these leaves, in the same way as they were formed from the 

 stem, and these secondary rays of a whorl may again pro- 

 duce rays of a higher order. The successive whorls of a 

 stem alternate in such a manner, that the oldest leaves of a 

 whorl, which have the branches in their axils, are arranged 



in a spiral line running round the stem. Each internode as fi g ure >; at d are the rhizoids &"-, 

 a rule suffers a subsequent torsion in the same direction, first 

 A lateral shoot is always formed in the axil of the oldest 

 leaf of a whorl in Chara, and in the axils of the two 

 oldest leaves in Nitella ; the lateral shoots repeat the development of the main stem in 

 every detail (Fig. 30). It has been already said that the segmentation of the leaves is 

 like that of the stem ; they too consist of internodes which are at first very short (Fig. 

 30, B, y), but are eventually much elongated, and are separated by short transverse 

 disks, the leaf-nodes ; from these nodes the lateral leaflets (secondary rays) spring in 

 successive whorls, which are not alternate, but. are in a straight line one above 



'T whori) of 



