78 CHLOROPHYCEAE 



probably indicates polyploidy. The following diploid chromosome 

 numbers have been recorded : C. repens 8 + i, C. Suhriana 12+ i, 

 C. flavescens 24, C. flaccida 24, C. pellucida 32, C. glomerata 64. 



Cladophoraceae : Rhizoclonium (rhizo, root; clonium^ branch). 



Fig. 53- 



This genus is either marine, brackish or fresh water, several 

 marine species being found in great quantities on sand or mud 

 flats. The uniseriate filaments are simple or else possess short 

 septate or non-septate colourless rhizoidal branches. The threads 

 are smaller in diameter than those of the preceding genera, and the 



Fig. 53. Rhizoclonium. A, part of filaments of R. ripariuyn ( x 90). B, cell of 

 R. hieroglyphicum to show structure of chloroplast. (A, after Taylor; B, after 

 Fritsch.) 



number of nuclei per cell are also less, usually one to four, although 

 in the stouter species there may be as many as twenty-four. It has 

 been found that the number of nuclei contained depends on the 

 cubical contents of the cell, a feature of size and form that is 

 analogous to the phenomenon found in the higher plants. The 

 number of epiphytes may also influence the quantity of the nuclei. 

 The plants are attached at first but become free-living later, and in 

 this state some of the larger species are scarcely distinguishable 

 from small species of the related genus Chaetomorpha. Vegetative 

 reproduction is by means of biflagellate zoospores which in some 

 species are said to have unequal flagellae. Anisogamy similar to 



