490 



any prolifications ; forma cornucopiæ was first recorded by Lyng- 

 by e under the name of Scytosiphon intestinalis f. cornucopiæ, Hy- 

 drophyt, p. 67. 



var. micrococca (Kutz.) Rosenv. 1. c. p. 957 ; Ulva enteromorpha ; , 

 intestinalis Ih, micrococca Le Jolis, Liste p. 47; Enteromorpha saxi- 

 cola Simmons, Meeresalg., p. 272. 



Of this variety, I have found several quite typical specimens, 

 e. g. corresponding exactly to Ahlner's description of Enteromorpha 

 micrococca (1. c. p. 45). The specimens were small, 3 — 4 cm. in 

 length, often somewhat prolific, or branching. The cells were small, 

 3—5^ broad, and had in the transverse section an especially thick 

 inner wall so that the thailus was nearly 18-20 /< thick. From 

 these t} r pical specimens, the transition might be traced by quite 

 easy stages to the different varieties mentioned in the following, 

 such as var. genuina and var. minima. Tims, many specimens 

 were found, in which the cells were becoming by almost imper- 

 ceptible degrees larger, and the walls thinner, until they merged 

 quite evenly into var. minima. In other larger specimens, the cells 

 too became larger, thus forming an easy transition to var. genuina. 



The rather considerable material at my disposal has shown 

 me conclusively how much the inner wall af typical E. micrococca 

 really varies in thickness. I have found the casiest transition be- 

 tween specimens in which the inner wall was thick and others in 

 which both the walls were of the same thickness, and others again 

 in which the outer wall was the thickest; the latter character pro- 

 bably induced Si mm o ns to separate off the new species E. saxicola; 

 but my researches prove, as is no doubt sufilciently clear from the 

 preceding remarks, that the species E. saxicola cannot be main- 

 tained. To explain this more fully I mav add that it is not only 

 between the different specimens that such transitions occur, but 

 even in the same individual very often something similar may be 

 observed. A transverse section of the thallus shows, e. g., that the 

 outer and inner walls of the cell of the lowest part of the plant 

 are often almost of the same thickness; in the upper part only the 

 inner wall is specially thickened, while al the top it mav happen 

 thai neither wall shows any noticeable degree of thickness. I ob- 

 served something quite similar in the original specimen of E. saxi- 

 cola, in which even if the outer wall is sometimes thicker than the 

 inner, the reverse is also often the case. 



var. minima (Næg.) Rosenv. 1. c. p. 959. 



