216 



Chlorophycece 



been observed in one colony 1 . Even in the large colonies the cells 

 are distinctly arranged in groups of four, the cells of each group 

 being closely adherent except in the centre, where there is usually 

 a small quadrate or rhomboidal space. The cell-walls are smooth, 

 and each cell contains a single chloroplast with or without a 

 pyrenoid. Multiplication occurs by autocolonies of four cells pro- 

 duced by the cruciform division of the contents of a mother-cell. 

 Schmidle 2 has given a good account of this genus under the 

 name of ' Staurogenia,' and has also described the formation of 

 hypnospores. 



Chodat has separated the genus Lemmermannia from Crucigenia 



mainly owing to the absence of a 

 pyrenoid from the chloroplast. For 

 the present I prefer to regard the two 

 as identical. There is no difference 

 in the structure of the colonies and 

 the mode of multiplication is pre- 

 cisely the same in each, the daughter- 

 cells persistently remaining as parts 

 of the mother-colony in several 

 species of Grucigenia as well as in 

 Lemmermannia. In all the speci- 

 mens I have observed of Crucigenia 

 Tetrapedia, which was the plant upon 

 which Chodat founded the genus 

 Lemmermannia 3 , there was the same 

 small gap in the centre of each group 

 of four cells that is present in all 

 other species of Crucigenia. 



C. rectangularis (Nag.) Gay is the most frequent species of the genus; 

 length of cells 5 9 p, ; breadth 4 6 p. ; fig. 90 A C. C. quadrata Morren 

 1830 ( = 1C. triangularis Chod. 1900) is a much rarer species; diam. cells 

 55-5 p. ; fig. 90 D and E. C. Tetrapedia (Kirchn.) W. & G. S. West 4 

 ( Lemmermannia emarginata Chod.) is known from the plankton of Lough 



1 West & G. S. West in Ann. Bot. xii, 1898, p. 36. 



2 Schmidle in Berichte Deutsch. Bot. Gesellsch. 1900, Bd xviii, pp. 149157. 



3 Under the heading of Lemmermannia emarginata, Chodat (in Beitrage zur 

 Krypt.-fl. Schweiz, Bd I, Heft 3, 1902, p. 222) makes some irrelevant remarks 

 concerning Tetraedron pentaedrica W. & G. S. West (which, for some reason, he 

 seems to think was described as a Tetrapedia !) and Tetrapedia morsa W. & (Jr. S. 

 West, which clearly show that he is quite unacquainted with either the published 

 descriptions or figures of the plants in question. 



4 West & G. S. West in Trans. Boy. Irish Acad. vol. xxxii, sect. B, part i, 1902, p. 62. 



Fig. 90. A C, Crucigenia rect- 

 angularis (Nag.) Gay, from Lough 

 Shannacloontippen, Galway, Ire- 

 land; C, with formation of auto- 

 spores. D and E, C. quadrata 

 Morren, from Settle, W. Yorks. F, 

 C. Tetrapedia (Kirchn.) W. & G. S. 

 West, from plankton of L. Neagh, 

 Ireland. G and H, Tetrastrum 

 Staurogeniceforme (Schrod.) Chod., 

 from near Bievaulx Abbey, N. 

 Yorks. (All x520.) 



