Ch lo i '0 theciacese 



407 



The geiiera are: Botryococcus Kiitzing, 1849 [ = Inejfigittta W. & G. S. West, 1897; 

 em. 1903; Botryomonas Schmidle, 1899; Botryodictyon Lemmermann, 1903]; Stichoglcea 

 Chodat, 1897 [inclus. Oodesmus Schinidle, 1902]; Askenasyella Schruidle, 1902 [ = Actino- 

 botr-ys W. & G. S. West, 1905]. 



Botryococcus Braunii Kiitz. is a very abundant Alga, occurring in hogs, ditches, tanks, 

 water-butts, ponds and lakes, but it is in the plankton of lakes that it attains its greatest 

 development. It is equally abundant in both temperate and tropical regions, and whereas 

 in bogs and pools the colonies rarely exceed 80 100 p in diameter, in the plankton they 

 may attain a diameter of 1 mm. (or even more). The large colonies are very oily and in 

 calm weather they float in great numbers at the surface of the water. In the late summer, 

 when the oil becomes brick- red, the waters of an entire lake may become tinged with a red 

 colour. This red colouration of the waters of lakes owing to a vast abundance of colonies 

 of Botryococcus Braunii has been observed in England, Switzerland and Central Africa. 



Family Chlorotheciacese. 



The Algre of this family are all unicellular epiphytes, mostly gregarious in 

 habit. The cells are subglobose, ovoid, ellipsoid or sometimes rather elongated 

 and acuminate at the apex. They are attached by a stalk of variable length 

 at the base of which is a more or less conspicuous disc. The stalk and disc 

 form the basal part of the cell-wall, so that the 

 attachment of the cells is of an entirely different 

 character from that which occurs in Peroniella and 

 Stipitococcus. Each cell contains from two to many 

 parietal chromatophores. The two known genera of 

 the family were described by Borzi and it is to him, 

 especially in his later work (Borzi, '95), that we owe 

 our knowledge of their life-histories. Cell-division 

 does not occur. On the reproduction of Ghlorothecium 

 there is an increase in the size of the cell followed 

 by a division of the protoplast which results in the 

 formation of a number (24 or more) of aplanospores. 

 These are liberated by the dissolution of the mother-cell-wall and at once 

 become zoogonidangia, setting free either two or four zoogonidia. The latter 

 come to rest and grow into new plants, or they may be facultative gametes 

 and conjugate in pairs. In Characiopsis reproduction usually occurs by 

 zoogonidia, of which four or eight are formed in each cell. At other times 

 several or many aplanospores may be formed and, as in Chlorothecium, on 

 liberation they immediately become gametangia which set free two or four 

 gametes. In both genera the zygospores do not rest, but at once produce 

 zoogonidia. 



The genera are : Chlorothecium Borzi, 1885, and Characiopsis Borzi, 1895. Species of 

 Characiopsis are not rare, but very little is known concerning Chlorothecium other than the 

 observations of its original describer. Printz ('14) has recorded it from Norway. The 



Fig. 258. A, Characiopsis 

 minuta (A. Br.) Borzi. 

 B I), Ch. turgida W. & 

 G. S. West. All x 500. 



