ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 189 



so to control the light that normal copulation takes place instead of the 

 springing apart of the cells. Single brightly lighted filaments show no 

 spore formation in the separated cells : they either die or grow into 

 new filaments. The author assumes, therefore, that the mutual influence 

 gained by the intertwining of the filaments is sufficient, and suggests 

 that this may be of a chemical nature. The spores must, therefore, be 

 regarded as parthenospores. 



Siphonales.* — R. Mirande writes an exhaustive treatise on the 

 chemical composition of the membrane of Siphonales and of the " mor- 

 cellement" of the thallus. His general conclusions are shortly sum- 

 marized as follows : — 



1. As to the chemical composition of the membrane, three different 

 types can be distinguished, (a) Membrane formed principally of callose 

 intimately associated with pectic compounds without appreciable trace 

 of cellulose (Caulerpa) ; (b) membranes formed principally of callose 

 associated with pectic compounds but with cellulose present in very 

 feeble proportion (Bryopsis) ; (e) membrane formed of cellulose asso- 

 ciated with pectic compounds with the absence of callose ( Vaucheria). 



2. The " morcellement " of the protoplasmic contents : — (a) This 

 phenomenon respects as a rule the continuous structure characteristic 

 of the group, and ends at the " fraction nement " (dismemberment) of the 

 alga into several new individuals ; but in certain cases it may resemble, 

 from the physiological point of view, a true " cloisonnement " (parti- 

 tioning), as in Codium ; (b) from the anatomical point of view it always 

 appears very different from the "cloisonnement" which has been de- 

 scribed for plants with uninucleate or plurinucleate cells, ,and the mem- 

 branous formations which result therefrom, can in a measure be 

 interpreted as cicatricial productions ; (c) it is usually accompanied, in 

 the groups of Siphonales, where callose is a fundamental substance of 

 the membrane, by a thickening or " gelification " of the primitive mem- 

 brane of the mother-plant ; this thickening or " gelification " is absent 

 in algae with a purely celluloso-pectic membrane ; (d) finally, attention is 

 drawn to the remarkable analogies presented by the mechanism of 

 "morcellement" in the genera Bryopsis, Derbesia, and Codium. 



3. From the systematic point of view : The chemical composition 

 of the membrane, although susceptible to slight variations, is none the 

 less a comparable character in its entirety between neighbouring species : 

 this character may prove to be of service in studying the classification 

 of the group. 



Characese of Bulgaria. f — S. Petkoff publishes a list of Characeae 

 from Bulgaria, which includes twenty-eight forms divided among a 

 half -score or so of species. C.foztida is the most widely distributed 

 species, occurring in twenty-six habitats and being represented by nine 

 different forms. Critical notes of structure and measurements are given. 



* Ann. Sci. Nat. Bot., ser. 9, xviii. (1913) pp. 147-64 (figs, in text). 

 t Nuov. Notar., xxv. (1914) pp. 35-56. 



April 15th, 191^ o 



