240 Chlorophycece 



gametangium, or much smaller than the zoogonidia and produced 

 in numbers from a gametangium. 



In some of these plants the colony has no definite form, but in 

 others the- cells, although irregularly grouped, are contained in a 

 mucous mass which invariably assumes a definite shape. 



The family can be divided into three sub-families, in each of which the 

 mucus may be indefinite or developed in accordance with some definite plan. 

 Sub-family I. Palmellece. Cells irregularly grouped within a 

 structureless mass of mucus. 



Sub-family II. Tetrasporece. Cells grouped in fours or sometimes 

 irregularly disposed at the periphery of a structureless mass of mucus. 

 Each cell with two pseudocilia. 



Sub-family III. Oloeocystidece. Cells grouped in twos or fours 

 within a lamellose mucous investment. 



Sub-family I. PALMELLE.E. 



This sub-family is characterised by the large number of globose 

 cells which are irregularly grouped within a structureless mass of 

 mucus. The latter is usually of indefinite extent, but in Palmo- 

 dactylon it is more or less cylindrical and often much branched. 

 The cell-walls are generally firm and thin, and in Schizochlamys the 

 outer layers are periodically thrown off in one or several pieces. 



Genus Palmella Lyngb., 1819. The cells are spherical, with 

 thin cell-walls, and they are surrounded by mucous coats which 

 have fused to form an indefinite mass of jelly. The parietal 

 chloroplast contains a pyrenoid. Multiplication takes place by 

 repeated bipartitions of the cells in all directions of space, ac- 

 companied by an extreme gelatinization of the mother-cell-walls. 

 Reproduction occurs by macrozoogonidia, by microzoogonidia, and 

 by small isogamous planogametes. 



One of the few true species of this genus is P. miniata Leibl., which occurs 

 as a mucous expansion of a brick-red colour on damp ground, wet rocks, etc. ; 

 diam. of cells 3 5 p.. P. mucosa Kiitz. and P. hyalina Breb. are aquatic 

 species of a green colour ; the former may possibly be a state of Tetraspora. 



Genus Palmodactylon Nag., 1849. This is a well-marked 

 genus of the Palmellea3, differing from Palmella mainly in the 

 definite form of the enveloping jelly. The chloroplast is parietal and 

 irregularly lobed, but is destitute of a pyrenoid. Multiplication 

 of the cells takes place in all directions, but preponderates in 



