Manchester Memoirs, Vol. Ivii. fipis), No. 0. 5 



the tetraspores were produced without chromosome 

 reduction, and, if functional, would give rise to a second 

 haploid generation. ( Vide Fig. 2.) 



This evidence was in part provided by a further 

 supply of material from Plymouth, which, besides con- 

 taining another plant with oogonial "sori" and tetra- 

 spores, also furnished four specimens in which antheridia 

 and tetraspores were associated on the same thallus 

 {Fig. 3). The very fact of the existence of antheridial 

 material, and also its association with that providing 

 oogonia, seems to suggest that the sexual organs functioned 

 normally. 



This view also receives some support from the occur- 

 rence of similar abnormalities in the Florideai. I have 

 observed both tetraspores and antheridia, and tetraspores 

 and all stages of cystocarpic development on the same 

 plant of Polysiphonia fastigiata and on a species of 

 Ceraniium,^ so that here at least the sexual organs are 

 obviously functional. 



Similar cases are recorded by Yamanouchi (6) as 

 occasionally occurring in Polysiphonia violacea, and he 

 suggests that the four cells derived from the tetraspore 

 mother-cell behave as monospores ; in other words, the 

 nucleus of the mother-cell, being haploid, does not undergo 

 meiotic division, but produces a second series of haploid 

 daughter plants. He thus adopts the view stated here as 

 the most probable for Dictyota. Harvey-Gibson (2), in 

 a short paper dealing chiefly with additions to the list of 

 marine alga^ in the L. M. B. C. area, also refers to similar 

 abnormalities in Ectocarpus confervoides among the Phaso- 

 phycea:;, and in Chylodadia kaliforiiiis, Callithamnion 

 baileyi, SperiiiotJianinion turneri and a number of other 

 Florideae, and states that among the plants of Polysiphonia 

 * These were glycerine-jelly mounts of material collected at Abeiystwyth. 



