234 BOTANICAL GAZETTE [September 



of g}^nodioecious plants. His studies in the inheritance of these plants had led 

 him to believe that some plants which he had classed as pistillate were really 

 bisporangiatCj and he now finds support for this conclusion in the fact that lessened 

 nutrition (using the term in its widest sense) decreases the development of the 

 stamenSj and, in the cases more nearly approaching starvation, suppresses them. 

 Gynomonoecious individuals give evidence for the same fact in that the bispoi'an- 

 giate flowers occupy the most advantageous places in the inflorescence, and appear 

 in the greatest proportion at the height of the flowering season, the earlier and 

 especially the later flowers being largely or entirely monosporangiate. The truly 

 pistillate plants cannot be made to produce bisporangiate flowers through increased 

 nourishment. This is held to support the author's view that the pistillate form 

 in gynodioecious species and the staminate form in androdioecious species are 

 fundamentally distinct and have arisen from the original bisporangiate forms by 

 mutation, and that they are not to be accounted for as the gradual accumulations 

 of minor advantageous fluctuations, nor as due in any way to ordinary physiologi- 

 cal response. There is some indication of the presence of distinct "lines" in 

 Satureia hortensis, in Johaxxsen's sense. Correxs. adheres strictly to the view 

 that nothing heritable can originate except through mutation, holding with 

 Nageli and others that the essence of mutation lies not in the size of the step but 

 in its heritability. — G. H. Shull. 



Halophytlsm. — From his study of the flora of the sea coast at Cagliari, Casu^ 

 found three features which appeared to depend upon the presence of marine salts 

 in the soil: (i) the sporadic distribution of the plants and their general dwarfing; 

 (2) the prevalence of herbaceous over woody plants in number and extension of 

 species; (3) the prevalent ubiquity of certain species in contact with saline solutions. 

 In order to elucidate these points, he has made a special physico-chemical study 

 'of the soil of the beach and shore at the surface and at various depths, both w^hen 

 seeds were just germinating and when plants were growing, and has compared 



composition 



After summarizing the very 



contradictory statements made by other observers, which are due, he thinks, to 



mi 



to study the physiological resistance of plants to sea salts under natural conditions. 

 His results agree in showing that the phenomena named above are quite independ- 

 ent of the toxic or the nutritive value of the salts and are rather a multiform effect 

 of more general conditions. Thus, by way of summary he says: the presence 

 of germinating plants at the time of the reactivation of vegetation depends on the 

 presence of organic residues at the surface of the soil and on its hardness; the 

 true factor of distribution of the species is the physico-chemical structure of the 

 soil; the prevalence of herbs and dwarfing are due to impoverishment of the soil; 

 neither the percentage of salts in contact with the roots nor that of any single salt 



9 Casu, a., Contribuzione alio studio della flora delle saline di Cagliari. Parte III. 

 Resistenza fisiologica della flora delle saline aU' azione del sale marino. Annali di 

 Botanica 5:273-354. 1907. 



