EUPHYCOPHYTA 



73 



gether with rhizoids from one or two basal cells. The thallus, 

 which is often invested by a gelatinous matrix of pectins, possesses 

 a main axis composed of large barrel-shaped cells, each containing 

 a small, entire or reticulate chloroplast and several pyrenoids. This 

 axis is primarily for support, and it bears much branched laterals 



Fig. 38 Draparnaldia. A, portion of plant ( x f). B, same en- 

 larged, C, rhizoids in D. plumosa. D, aplanospores of D. glomerata. 

 (A, Bj D, after Oltmanns; C, after Fritsch.) 



that normally grow out in tufts, the short cells composing the 

 laterals being almost wholly filled by one entire chloroplast con- 

 taining a single pyrenoid. The apices of these branches, which 

 perform the functions of assimilation and reproduction, are often 

 prolonged into a hair. In some species rhizoids develop at the base 

 of the branches and grow downwards, thus clothing the main axis 

 with a pseudo-cortex, but normal growth is generally restricted to 

 a few cells of the thallus. When grown in culture with increased 

 carbon dioxide or additional nitrate the plants take on a form very 

 like that of Stigeoclonium (cf. above). Asexual reproduction is by 



