ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 217 



to rest, rounds itself off, becomes enclosed in a membrane, and passes 

 into the condition of an embryospore. ' Then the embryospore doubles 

 its diameter without changing its form and multiphes its chromatophore, 

 while the nucleus remains single. It then becomes elongated into a 

 tube of the same width or narrower, and a length of several times its 

 diameter. The zoospore contents soon leave the posterior extremity 

 and accumulate in the young extremity. They break the membrane 

 and escape in a naked uninucleate mass, slightly elongated, which rests 

 on the opening of the tube of the empty embryospore, becomes 

 surrounded with a membrane, and grows rapidly. This is the orgin of 

 the plantlet. This plantlet applies itself to, and moulds itself so exactly 

 on, the mouth of the empty tube, that it looks as if the contents of the 

 embryospore had simply moved up and separated themselves by a cell- 

 wall from the abandoned posterior portion. One zoospore provides in 

 this way one individual. This may be regarded as the normal mode of 

 germination. If the embryospore divides its nucleus in two and a 

 dividing wall is formed, the contents of the anterior cell escape and 

 germinate. If it becomes a monosiphonous filament of several uni- 

 nucleate cells, it is generally the contents of the anterior cell again 

 w^hich provides the plantlet ; and if the rest of the filament continues 

 to grow instead of perishing, it may produce another backward plant. 

 Finally, there are cases of slow^-growing cultures, in which the embryo- 

 spore emits upright branches, each of which may produce a plantlet by 

 the same process. In this way a zoospore produces at least two 

 individuals. 



The development of the plantlet begins at once and is continued 

 unceasingly. The details are as follows : — The unicellular plant, as a 

 rule adhering to the neck of the embryospore membrane, divides trans- 

 versely alfout the middle ; each half increases in size and again divides 

 transversely. In this quadricellular plant the two superior cells are 

 broader than the others and divide by a median longitudinal wall. 

 Their importance is,- however, less than that of the inferior cells which 

 each divided into two. The further divisions of these cells are described 

 and figured, and the part that each plays in the further development of 

 the plant is indicated. The growth of the plantlet is simultaneously 

 stipofrondral and intercalary, as in the adult plant. 



Heterogamic Sexuality of Saccorhiza bulbosa.* — C. Sauvageau 

 records for the first time among the Laminariaceae a heterogamic 

 sexuality with alternation of generations. In a previous paper he 

 describes the development of S. Imlhosa,^ and notes the presence of a 

 naked mass of protoplasm ; this mass is an oosphere, and the embryo- 

 spore, either unicellular or pluricellular, which provides it is the female 

 gametophyte. With this there appears constantly a male gametophyte 

 smaller in size. The author made his first cultures in March 1914. They 

 were repeated many times and were always free from Phjeosporeae. 

 Nevertheless, although all the zoospores appeared identical, there 

 always appeared several days after dehiscence an unknown brown alga. 



* Gomptes Eendus, clxi. (1915) pp. 796-9, 

 t Gomptes Rendus, clxi. (1915) pk 740. 



