— 106 — 



Microspora, fat in Conferva) were found to accuraulate in 

 some of tlie filaments (1) , and thèse undoubtedly provided the 

 basis from which subséquent récupération took place. It will 

 altogether be gathered from the list given on p. 90 that, except 

 in a l'ew forms, spore- formation wasrarely observed in Barton's 

 pond, a resuit similar to that obtained for Abbot's pool. It can 

 scarcelv be supposed that in such an extcnsive séries as ours the 

 formation of spores lias been frequently overlooked, and we 

 must therefore concliide that in pièces of water like Abbot's 

 pool and Barton's pond a few individuals always manage to 

 persist during the minimum period and give rise to a new maxi- 

 mum as soon as the conditions become favourable. 



G. — Systematic notes. 



I. — Spirogyra cataeniformis (Hass.), Kûtz. This spec- 

 ies, which is verv abundant in Barton's pond, mostlv showed 

 the typical characteristics defined by P 'etit (Sp ir v g yr a desenvi- 

 rons de Paris, 1880, p. 17, tab. III, fig. 0-12), except that 

 the inflation of the fructifying cells was often more pronounced 

 than shown in bis figures. We bave however also observed 

 cases in which scarcely any inflation was discernible and others 

 in which it was rather one-sided (cf. also Borge, Al g en d. 

 ersten Regnellschen Eocped. &] , p. 280). Only scalariform 

 conjugation was observed. 



II. — Spirogyra quadrata (Hass.), Petit. Typical material 

 of this species was often met with and conformed well to Petit's 

 figures (loc. cit., pi. I, fig. 13). The conjugation was chiefly 

 latéral. Occasional filaments showed considérable resemblance 

 to .S 1 , inflata (Vauch ), Rab. in having the fructifving cells 

 shorter than the végétative ones and in lacking the pronounced 

 rectangular form of the cells containing the zygospores. Fur- 

 tlier, occasional filaments were observed in which a larger or 

 smaller number of cells exhibited two instead of one spiral (3) , 

 and we figure a case in which conjugation wàsobserved betwf en 

 filaments with two and one spiral respectively (p. 107, fig. C). As a 

 resuit of our more extended investigations wefeel convinced that 



(1) The same is true also of Eunotia Arcus. 



(2) Arkivfdr Botmik,Band 1, 1903. 



(3) <'f. also Miaula, KryptogamenH. von Deutschland, Deutsch-Oesterreich 

 a. d. Sckweiz, II, 1, 1907, p. 570. 



