;82 



CHARACE.E. 



The nodes are the part from which all the lateral members of the Characese 

 originate. The root-like structures or Rhizoids spring from the outer cells of the 

 lower nodes of the primary shoot, and consist of long hyaline sacs growing 

 obliquely downwards, and elongating only at their apex. They are formed by the 

 outgrowth of flat cells at the circumference of the node, and are therefore at- 

 tached to it by a broad base; but these bases of the' stouter rhizoids themselves 

 divide still further, giving rise, especially at the upper margin, to small flat cells 

 from which slender rhizoids are developed. The rhizoidal tubes are segmented by 

 only a few septa which lie far below the growing apex, and have at first an oblique 

 position. The two adjoining cells abut one another like two human feet placed 

 sole to sole. The branching always proceeds only from the lower end of the 



upper cell (Fig. 202, B) ; a swelling is here 

 formed which becomes cut off" by a wall, and 

 by further division produces several cells which 

 grow into branches ; these therefore stand on 

 one side like a tuft. The tubular cells com- 

 posing the rhizoids attain a length of frorn several 

 millimetres to more than two centimetres, with 

 a thickness of from ^^ to j\y mm. 



The Vegetative {asexual) Reproduction of 

 Characeae always proceeds at the nodes, and 

 has three modifications: — (i) Nodular formations 

 called Bulbils which occur in Chara stelUgera. 

 They are isolated underground nodes with greatly 

 abbreviated whorls of leaves of beautiful regu- 

 larity ; their cells are densely filled with starch 

 and other fornmtive materials; new plants are pro- 

 duced from shoots laterally developed. (2) The 

 Branches with naked base of Pringsheim. These 

 are formed on old hibernating or on cut nodes 

 of Chara in the axils not only of the oldest but 

 also of the younger leaves of a w^iorl, and are in fact only slightly diff"erent from the 

 normal branches, the greatest difference being in the partial or entire absence of the 

 cortex of the lower internode and of the first whorl of leaves. The cortical lobes 

 which descend from the first node of the branch often become detached from 

 the internode and grow free, curling upwards, while the leaves of the lowermost 

 whorl often do not form nodes. (3) The Pro-embiyonic Branches. These spring, 

 together with the last, from the nodes of the stem, but are essentially different 

 from the branches, and have a similar structure to the pro-embryos which proceed 

 from the spores. Like the last, they have only been observed in Chara fragilis 

 (by Pringsheim). A cell of the node becomes elevated, and growls into a tube, 

 and its apex becomes separated by a septum. In this growing terminal cell 

 further divisions take place, till the 'apex of the pro-embryo' which proceeds from 

 it consists of a row of from three to six cells. Beneath the apex of the pro-embryo 

 (Fig. 203, C, a, b) the tube swells, and the distended part becomes separated by 

 a septum as a cell, which Pringsheim calls the * bud -rudiment,' (Fig. 203, C, 



I-IG. 2U2.— Rhizoids of Chrra fragilis ; A end 

 in process of development ; B a 'joint,' the lower 

 part of the upper cell is branching (after Prings- 

 heim, X 240). The arrows indicate the direction of 

 the currents of protoplasm. 



