BOTANY 371 



Sisyrinchium indicates a widespread occurrence of no taxonomic 

 significance. 



Genetics. — -The effect of selection within pure fines has again 

 been attempted, this time with Pestalozzia Guepini, one of the 

 fungi imperfecti, as the subject of investigation. The selec- 

 tions were made according to two plans. In the one series 

 the selection was based on the divergence in the progeny means 

 so that the usual visible characteristics were ignored and the 

 performance of the progeny used as the criterion of selection. 

 In the second series the usual method of selection by visible 

 characters was adopted. The characters used were length of 

 spore and length of spore appendage, the selection being main- 

 tained for 10 and 25 generations in one experiment, and 10 and 

 6 generations in a second {Genetics, pp. 142-201, 1922). 



Neither method was effective in establishing a distinct 

 line within the pure strain. Mutations were observed, though 

 infrequent, and it is interesting to note that a mutation with 

 exceptionally long spore appendages appeared in a pure line 

 which was being selected for diminished length of spore 

 appendages, and it is pointed out that mutations in the same 

 sense as the selection might well account for the positive 

 results obtained by some workers. 



Floral Morphology species of the genus Marcgravia have 

 been regarded as affording striking examples of a pollination 

 mechanism adapted to the agency of humming birds which 

 visit the flowers for the sake of the sugary fluid in the pitcher- 

 like bracts borne below the flowers, or ior the sake of the 

 flies which visit these pitchers. Bailey {Amer.^Jonr. Bot., 

 pp. 320-84, 1922) has studied two species of this genus, de- 

 scribed as new, in the field, and finds no grounds for believing 

 the flowers to be pollinated by birds which approach the 

 inflorescences from above even in species with downwardly 

 directed flowers. On the contrary, his observations and 

 experiments lead him to the conclusion that both the species 

 studied, and probably also AI. umbellata, are self-pollinated. 



PLANT PHYSIOLOGY. By Cyril West, B.A.. D.Sc, Low Temperature 

 Research Station, Cambridge (Plant Physiology Committee). 



After-ripening, Dormmicy, and Methods of Terminating the 

 Dormant Period of Seeds. — During the last two or three years 

 much attention has been directed to the subject of after- 

 ripening and dormancy of seeds, especially by American 

 botanists. But although an intensive study has been made 

 of the chemical and physical changes which take place in 

 dormant seeds of various plants, not only in the embryo itself, 

 but also in the structures which make up the seed coat, we 



