9 



and contain a few chloroplasts and a delicate protoplasmic 

 lining. They do not, indeed, differ from the general 

 hyphse, of which the main mass of the plant is composed. 

 Each has a definite and fairly thick wall, and several 

 nuclei in the peripheral lining of protoplasm. The rhiz- 

 oidal, as well as the medullary hyphoe, are sub-divided at 

 intervals by the formation of annular thickenings on the 

 inside of the walls. The annulus gradually increases until 

 the lumen is completely occluded. Such occlusion is 

 figured at fig. 2, PI. I. ; figs. 10 and 14, PL II. ; figs. 17, 

 18, and 19, PI. III. 



The chloroplasts in the plant generally are very minute 

 and extremely numerous, and usually associated in strings 

 or clusters, especially in the lateral palisade branches. 



The nuclei, described first by Arcangeli (Sul alcune 

 Alghe del gruppo delle Celoblastee, Nuova gior. hot., 

 VI.), but not known to him as nuclei, have been the 

 subject of investigation by Schmitz {Sitz. d. natur. Gesell. 

 zu Halle, 1878) and Berthold (Zur Kenntnis der Sipho- 

 neen und Bangiaceen, Mitt. Zool. Stat. Neapel, 1880). 

 We have not ourselves followed the division of the nuclei, 

 and so incorporate a brief abstract of Berthold's obser- 

 vations. 



Berthold studied the division of the nuclei in the 

 palisade " cells " where, in the basal region, owing to the 

 small number of chloroplasts, they can be easily made 

 out. He found them to be much flattened, oval or ellip- 

 tical in outline, and sometimes pointed at one end. Each 

 contains two or three nucleoli. The nuclei are usually 

 about 15 jj- in length and 6 jj- broad, and each possesses a 

 clearly defined nuclear membrane. Berthold was unable 

 to study the very earliest stages in the division, but the 

 phenomena observed from an early stage to the end of the 

 division occupied from 3 to 4 hours. During the entire 



