130 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



In a paper on the life-history of Polysiphonia 

 violacea, Yamanouchi (Bot. Gaz. Vol. XLII) demon- 

 strates a regular alternation of generations in that species 

 between a gametophyte, the nuclei of whose cells have 

 20 chromosomes, and a sporophyte whose nuclei have 

 40 chromosomes. At the same time he records under 

 the head of "Abnormalities" the occurrence of tetra- 

 gonidia on cystocarpic or antheridial plants, and refers 

 to similar cases noted by Lotsy in Chylocladia 

 kaliformis, and by Davis in Syermothamnion turneri 

 and Callith amnion baileyi. He adds " such cases should 

 be carefully investigated to determine whether true 

 tetraspores are present or whether the structures are not 

 really of the nature of monospores, as in Polysiphonia, 

 and developed with a suppression of reduction 

 phenomena." In the plants of Polysiphonia violacea 

 collected by us at Port Erin in 1912, cystocarpia and 

 gonidangia were frequently present on the same branch, 

 and the number of cases we met with, both in that 

 species and in other genera, in our opinion scarcely 

 justifies the view that all of these are to be regarded as 

 "abnormalities." We have also found sexual and 

 asexual organs on the same branch in Lophothalia 

 byssoides, Callithamnion hookeri, C. tetragonum, C. 

 corymbosum and in Hypnaea valentiae, a species obtained 

 from the Soudan litoral. Mr. A. D. Cotton informs us 

 that he has noted the same joint occurrence of sexual 

 and asexual organs on the same plant in Laurencia 

 hybrida and in an undetermined species of Callithamnion. 

 Indeed, we have been forced to the opinion that the 

 constant alternation of sexual and asexual stages, as 

 emphasised by Yamanouchi, is open to criticism, and 

 that the occurrence of tetragonidia, cystocarpia and 

 antheridia on the same plant is by no means an 

 exceptional phenomenon. 



