NITBLLA HYALINA. 129 



The only locality in the British Isles at present recorded 

 for N. hyalina, Looe Pool, near Helston^ is a large piece of 

 water, the western end of which is only divided from the sea 

 by a narrow sand-bar. Here the plant was found in great 

 abundance at the end of August, 1898. It was still there in 

 1914. 



[N. ornithopoda Braun, a monoecious species having the 

 ultimate rays of the branchlets 3-5-celled, occurs in the 

 South West of France; and N, Dixonii H. & J. Groves, 

 which is very similar in character, but dioecious, has been 

 found in the extreme South of Portugal. Both these species 

 belong to Braun's section Polyarthrodactylse, most of the 

 members of which are natives of the southern hemisphere.] 



Genus 2. TOLYPELLA Leonhardi. 



Nitella sect, caudatss Braun in N. Denks. Schweiz. Ges. Naturw. X, 



p. 11 (1849). 

 Nitella sub-gen. Tolypella Beaun in Hooker's Jonvn. Bot. I, pp. 194 & 



199 (1849) ex parte ; in Monatsb. Akad. Berl. 1867, p. 797 (1868). 

 Nitella sect. Pseudo-bracteatse Wallman Forsok syst. Charac. p. 39 



(1853) pro parte ; Transl. p. 33 (1856). 

 Tolypella Leonhardi in Lotos, Xlll, p. 72 (1863) ; in Verb. Naturf. 

 ver. Briinn, II, p. 158 (1864). 

 Wahlstedt Mon. Sver. & Norg. Charac. p. 21 (1875). 

 Beatjn in Coka, Krypt. Scbles. I, p. 400 (1876). 

 Bbatjn & NoBDSTEDT Eragm. Mon. Charac. p. 93 (1882). 

 MiGTJLA Die Characeen,p. 198 (1890) ; Syn. Cbarac. Europ. p. 53 (1898). 



Branches frequently more than two at a stem-node. 

 Sterile branchlets simple or forked ; fertile branchlets 

 forked with very unequal rays. Antheridia and oogonia 

 frequently long stalked, produced laterally at the nodes 

 of the branchlets, also often in considerable number at 

 the base of the whorls. Oogonia clustered. Oospore 

 subglobose or broadly ellipsoid, terete in section. 



A compact natural genus, distinguished from Nitella 

 by the lateral position of the antheridium, by the 

 ripe oospore not being laterally flattened, and by the 

 very unequal length of the branchlet-rays. The pro- 

 duction of reproductive organs at the base of the 

 whorl which is quite common in Tolypella is a rare 

 occurrence in Nitella. In the constantly monopodial 

 growth of the branchlets, and the terete oospore it 



VOL. I. 9 



