110 



H. simulans. As distinctions between the species besides differ- 

 ences in their outer appearance Howe also lays stress upon histo- 

 logical characters, namely the peripheral utricles, as after Howe 

 these in H.tridens are 49 — 77, « in average maximum diameter 

 while in H. monile and H. simulans they are 30 — 40/^ in average 

 maximum diameter, these two species being otherwise kept 

 separated by the forms of the joints which are mostly subterete 

 in the first mentioned, discoid in the last. 



Fig. 88. Halimeda incmssata (Ellis et Solander) Lamx. 



Three different forms from Krause's Lagoon (my collections nr. 1484). 



Regarding the habit of these plants, a and c may be referred to var. typica, 



h to var. monilis. As pointed out in my paper 1. c. p. 139 the size of the 



peripheral utricles shows much variation. (About -h:\). 



Having now examined a very large number of specimens in 

 my collection I willingly admit that these characters in the differ- 

 ent forms very often agree with what Howe has found, in that 

 the peripheral utricles are large in specimens belonging to the 

 typical form and smaller in forms coming near to monile and 

 simulans. But just as intermediate stages occur in the outer appea- 

 rance of these forms, so we often also find specimens with large 

 and small cells intermingled or specimens in which the outer 

 form and the dimensions of the peripheral utricles point against 



