416 Literature 



plant ; if the cysts remain in the mud in the dark they become hypnocysts 

 and may rest for a long time, although when ultimately moistened they 

 at once become zoogonidangia. The zoogonidia always begin development in 

 the same way. On coming to rest they become rounded off and increase in 

 size. The nucleus begins division and there is soon a great increase in the 

 number of both nuclei and chromatophores. At this stage a delicate rhizoid 

 is developed. Subsequent development is variable and depends largely upon 

 external conditions, but finally vegetative plants are produced. 



Rostafinski & Woronin described a sexual reproduction by the fusion of isogametes, but 

 Klebs ('96) has shown that in all probability the life-histories of two organisms were 

 confused by those authors. 



Botrydium granulatum (L.) Grev. is a very local Alga and is not often observed because 

 the conditions necessary for the development of the vegetative plants only rarely obtain. 

 It is found almost exclusively upon drying-up mud turned out from ditches, canals, etc., or 

 on the drying bottom of a muddy pond. It seems highly probable that some form of 

 resting-spore of Botrydium^ probably a hypnocyst, is universally distributed in the mud of 

 fresh waters in temperate regions and also in many parts of the tropics, since the vegetative 

 plants almost invariably appear when such mud attains a certain degree of dry ness. 



There is a second species B. Wallrothii Kiitz. which differs in its thicker lamellate 

 cell-wall, in the characters of the rhizoidal part, and in other minor details. Klebs 

 regarded this species as a hypnosporangium-state of B. granulatum, but Iwanoff has given 

 good reasons for its retention as a separate species. 



LITERATURE CITED 



BLACKMAN, F. F. & TANSLEY, A. G. ('02). A Revision of the Classification of the Green 



Algse. New Phytologist, i, 1902. 

 BOHLIN, K. ('97). Studier ofver nagra slagten af Alggruppen Confervales Borzi. Bihang 



till K. Sv. Vet.-Akad. Handl. Bd. xxiii, no. 3, 1897. 

 BOHLIN, K. ('01 A). Utkast till de Grona Algeriias och Arkegoniaternas Fylogeni. 



Upsala, 1901. 

 BOHLIN, K. ('01 B). Etude sur la flore algologique d'eau douce des Agores. Bihang till K. 



Sv. Vet.-Akad. Handl. xxvii, no. 4, 1901. 

 BORZI, A. ('95). Studi Algologici. II. Palermo, 1895. 

 CHODAT, R. ('96). Sur la structure et la biologic de deux Algues pelagiques. Journ. de 



Botanique, 1896. 



CHODAT, R. ('08) in Bull, de 1'Herb. Boiss. 1908, p. 81. 

 DERBES, A. & SOLIER, A. J. J. ('56). Memoire sur quelques points de la physiologic des 



Algues, 1856. 

 GARDNER, N. L. ('10). Leuvenia, a new genus of Flagellates. Univ. of California 



Publications, Botany, iv, no. 4, May 1910. 

 HAZEN, T. E. ('02). The Ulotrichacese and Choetophoraceee of the United States. Memoirs 



Torr. Bot. Club, xi, no. 2, 1902. 

 HEERING, W. ('06). Die Siisswasseralgen Schleswig-Holsteins usw. 1 Teil : Einleitung. 



Heterokontse. Jahrb. Hamburgischen Wiss. Anstalten, xxiii, 1905 (1906). 



