76 



Ctilorophycece 



latter genus should undoubtedly be placed as a synonym of Hor- 

 miscia Fries. 



The best known species of the genus is U. zonata (Web. et Mohr.) Kiitz., 

 (tig. 20 A and B), which is widely distributed all over the British Islands, 

 occurring as bright green masses in streams, rivers, etc., more especially in 

 the early spring. The cells vary from 15 70 /x in diameter and the cell-walls 

 are very thick and lamellose. An abundant British species is U. subt Hi's Kiitz. 



Fig. 21. A F, Ulothri.r a-qualls Kiitz.; A D, from Putney Heath, Surrey; E and 

 F, from Mitcham Common, Surrey; A, filament showing escape of micro- 

 zoogonidia ; B D, germinating macrozoogonidia, C shows the same plants as 

 B 48 hours afterwards, D is much further advanced; E, portion of filament of 

 akinetes ; F shows two aplanospores which have taken exactly 14 days to 

 develop from ordinary vegetative cells. G, U. vyi///.s Kiitz. var. catceniformis 

 (Kiitz.) Rabenh., from near Bradford, W. Yorkshire, showing escape of macro- 

 zoogonidia. H, U. moniliformis Kiitz., from Wimbledon Common, Surrey ; 

 I, the same with akinetes. (All x 500. ) a, aplauospore ; ak, akinete ; za, macro- 

 zoogonidiura ; zi, microzoogonidium. 



(fig. 20 C F), the cells of which are as long as broad and from 4 8 fj. in 

 diameter. A variety of this species var. variabilis (Kiitz.) Kirch n. is 

 probably the most abundant member of the genus, being generally distributed 

 in the stagnant waters of ponds, ditches, troughs, rain-tubs, etc. It is a little 

 thicker than U. subtilis and the cells are lj 2j times longer than their 

 diameter. U. cequalis Kiitz. (fig. 21 A F) and U. moniliformis Kiitz. (fig. 21 

 H I) are other well-known species. 



Another Alga Sclnzomeris Leibldnii Kiitz. which I have only once seen, 

 from Stone Ghyll, Dodd Fell, N. Yorkshire, should perhaps be included here. 

 I am doubtful as to the exact determination of the Yorkshire specimens, but 

 they reminded one very much of a large Ulothrix zonata, attenuated both at 

 the apex and the base, the latter being fixed to rocks and stoues in the spray 

 of a waterfall. Longitudinal division of the cells had occurred at intervals, so 



