SPONDYLOSIUM. 219 



Geoyr. Distribution. Japan (var.). India. Ceylon. 

 Burma. Java. Australia. East and Central Africa (var.). 

 United States. W. Indies (var.). Guiana. Brazil. 

 Paraguay ( va r . ) . 



This species is very rare in Britain, and indeed in the whole 

 of Europe. There is only the one record of it for the British 

 Isles. 



The spore figured on PL CLX, fig. 16 is peculiar in having 

 been produced apparently from a single cell. The authors of 

 this Monograph were undecided whether it should be considered a 

 true zygospore or an aplanospore. In its external form it is 

 essentially similar to the zygospore of the variety micracanthum 

 of this species (see PL CLX, fig. 17). This variety is rather 

 more frequent than the type form, though it does not occur in 

 North Temperate regions. The normal zygospore of the typical 

 form has not vet been observed. 



Genus 23. SPONDYLOSIUM Breb. 1844. 



Breb. in Diet. univ. hist. nat. 4, 1844, p. 711 (Spondylotium). 



Kiitz. Spec. Alg. 1849, p. 189. 



De Bary, Conj. 1858, p. TO. 



Arch, in Pritch. Inf. 1861, p. 724. 



Kirchn. Alg. Schles. 1878, p. 133. 



De Toni, Syll. Alg. 1889, p. 792. 



Wille in Eiigler, Naturl. Pflanzenfam. 1890, p. 14. 



Turn. Freshw. Ate. E. India, 1893, p. 47. 



G. S. West, Brit. Freshw. Alg. 1904, p. 175. 



Leuronema \Yallich, Desm. Low. Bengal, 1860, p. 193. 



Cells usually small, or of medium size, flattened and 

 often deeply constricted with a narrow or open sinus ; 

 semicells variable in shape, often with broadly truncate 

 or concave apices ; in vertical view elliptical, triangular 

 or trilobed ; chloroplasts axile. Cells united to form 

 long filamentous colonies by the simple close apposition 

 of their apices, sometimes twisted and often enveloped 

 in mucilage. In one species the filaments are often 



O j- 



observed attached to other aquatic plants by means of 

 a short basal gelatinous cushion. 



o 



Zygospores usually globose and smooth, or with 

 simple spines. Lateral conjugation through the apices 



