256 RESEARCH SEMINAR. 



which necessarily belong to thalli diverse in character. Every 

 heterothallic species is an aggregate of two distinct strains 

 through the interaction of which zygospore production is brought 

 about. These sexual strains in an individual species show a 

 more or less marked differentiation in vegetative luxuriance which 

 may be designated by ( + ) and ( ) signs respectively. A proc- 

 ess of imperfect hybridization will occur between unlike strains 

 of different species. By taking advantage of this character it has 

 been possible to group together in two opposite series the strains 

 of all the heterothallic species under cultivation. When thus 

 grouped the ( ) strains will be in one series while the ( + ) will 

 be in the other. In the two series are represented the two sexes. 



August 8. The Algal Flora of the Gulf of Naples. By DR. 



BRADLEY M. DAVIS. 



This seminar considered the character and distribution of the 

 marine algae in the vicinity of Naples and was illustrated by a 

 collection. Comparisons were made with the flora of the Atlantic 

 coast of America south of Cape Cod which has some important 

 features in common with the Mediterranean. The opportunities 

 for botanical work in the zoological station at Naples were 

 described. 



