Microsporacece 



101 



Genus Microspora Thuret, 1850; em. Lagerh., 1888. 

 filaments are simple, con- 

 sisting of cylindrical or 

 slightly swollen cells. The 

 cell-walls are firm, fre- 

 quently distinctly lamel- 

 lose, and sometimes dis- 

 sociating into pieces 

 which appear H -shaped 

 in optical section, each 

 piece consisting of a trans- 

 verse wall and portions 

 of the lateral walls of two 

 adjacent cells. There is 

 one cell-nucleus. The 

 chloroplast is disposed on 

 the cell-walls as a more 

 or less reticulated mass. 

 Globular hypnospores are 

 produced, with thick walls, 

 usually one in each cell. 



The 



There are several widely 

 distributed species of this 

 genus in the British Islands. 

 M. floccosa (Vauch.) Thur. 

 and M. amoena(K.\itz.) Lagerh. 



Fig.37. A, Microspora amcena (Kiitz.) Lagerh., 

 from near Senens, Cornwall. B and C, M. ab- 

 breviata (Rabenh.) Lagerh. ; B from Tremethick 

 Moor and C from St Just, Cornwall. D, M. 

 pachyderma (Wille) Lagerh., from near Land's 

 End, Cornwall. E and F, forms of M. amcena 

 (Kiitz.) Lagerh.; E, from Shipley, W. Yorks., 

 to show the chloroplast; F, from New Forest, 

 Hants, a, aplanospores. (All x520.) E is 

 M. amcena var. crassior Hansg. 



(fig. 37 A, E and F) are the 

 most abundant and often occur in small ponds and horse-troughs. M. abbre- 

 viata (Rabenh.) Lagerh. (fig. 37 B and-C) and M. pachyderma (Wille) Lagerh. 

 (fig. 37 D) are not so frequent. 



Order VI. CLADOPHOBALES. 



In this order are included three families of green Algse which 

 bear close relationship to the Siphoneae and yet can scarcely be 

 relegated to that order. The thallus is simple or branched and 

 incompletely septate, each segment containing many nuclei and 

 numerous parietal chloroplasts, the latter containing single 

 pyrenoids. 



Asexual reproduction takes place by biciliated or quadriciliated 

 zoogonidia, by 'cysts,' or by special resting-spores (Pithophora) ; 



