STBUOTUBB AND DEVELOPMENT. 69 



ductive action " (l. c, p. 121). ""Weak electrical currents 

 may accelerate streaming, strong ones always retard it, 

 sudden shocks produce temporary cessation." (p. 192.) 



In the Oharophytes cyclosis is stated to persist 

 during the entire existence of the adult cell, permanent 

 cessation always indicating fatal injury. 



According to Goebel (' Physiol.' iii, pp. 165 and 174, 

 Transl.) the shoots of Ghara and Nitella show a fairly 

 strong negatively geotropic action and the internodes 

 show positive heliotropism in ordinary light. Haber- 

 landt states (' Physiol. PI. Anat.,' p. 608, Transl.) :— 

 " the positively geotropic rhizoids of certain species 

 of Ghara {0. fragilis, G. foetid a, G. aspera) contain, 

 near their tips, minute solid bodies of unknown 

 chemical composition {Glanz-Korperchen), which have 

 been shown by Giesenhagen to respond to the action 

 of gravity. Bach group of these bodies, together with 

 the associated cytoplasm, seems to represent the stato- 

 lith-apparatus of the rhizoid," 



A CONSPECTUS 



op the distinctive characteeistics 01' the oospoees and 

 Membeanbs op the British Oharophytes. 



The membrane referred to is ahcays the external coloured 

 membrane. " Fossulm " are the spaces lying between the ridges 

 of the oospore. By " granular density per \0 fx" is meant the 

 approximate number of granules in the fossulm lying along a 

 line 10 yu in length. 



I. Oospore laterally compressed^ ovoidal or orbicular ; 

 membrane thin or thick, flexible or semi-rigid; trans- 

 lucent or semi-opaque ; smooth, eruptive, or decorated. 



Nitella. 

 (1) Membrane thick and semi-rigid — 



(i) smooth or eruptive, undecorated, dark red. 



(a) oospore small (375-425 fx) . N. opaca. 



(b) oospore large (500-575 ju) . N.flexilip. 



