345 



that the published statements regarding the cytology of conjugation in 

 Zygnema are not at all in agreement with one another, and that much further 

 investigation is still required. 



It is necessary to consider the case of Zi/<jn<-iii crn-etorum (Kutss.) Hansg. separately. 

 This Alga has a world-wide distribution and in temperate countries it lives equally well in 



Fig. 215. Zygnema ericetorum (Kiitz.) Hansg. A and B, fully conjugated specimens; C, an 



early stage in conjugation ; 1) and E, stained specimens to show the chloroplast and nucleus. 



ch, chloroplast; cj, conjugation-canal; g, gametangium ; n, nucleus; py, pyrenoid; z, 



zygospore. AC, x425; D and E, x 1500. 



Note. A C were originally described under the name of Zygnema pachydermum W. & 



G. S. West. 



water or on damp heaths or peaty moors, not infrequently assuming a purple or violet 

 colour owing to the appearance of phycoporphyrin in the cell-sap. In 1858 De Bary 

 attempted to put the genus Zygogonium upon a new footing, including in it Z. erieetontm 



