BOTANY 23 



BOTAVT. By E. J. Salisbury, D.Sc, F.L.S., University College, London. 



Genetics. — An interesting dwarf mutation of Portulaca grandi- 

 flora which behaves as a recessive to the normal habit has been 

 investigated by Blakeslee {Genetics, July 1920). About 1-25 

 per cent, of these recessives produced branches which had 

 reverted to the normal type of growth with long internodes. 

 Both the dwarf and reverting branches of these plants were 

 *'selfed"; the former bred true, showing that the vegetative 

 mutation only affected the branches exhibiting external 

 change. The " selfed " reverted branches yielded both types 

 in the ratio of three normal to one dwarf, whilst back-crossed 

 to dwarf gave 1:1. 



In an extensive study of the protein content of maize 

 {Genetics, Nov. 1920), East and Jones find that the environ- 

 mental factors can raise or lower the total per cent, as much as 

 40 per cent. As a consequence of unit selection from a popu- 

 lation during twenty-three years at Illinois Agric. Exp. Sta., 

 high- and low- yield strains were obtained with an average 

 difference of nearly 6 per cent in protein. In five selected 

 strains seeds from the same cob showed variation coefficients 

 ranging from 5-72 ± 0-33 to 8*94 ± 0'47. The seeds borne by 

 hybrid plants are larger, more numerous, and contain a smaller 

 percentage of protein. Probably the factors involved are 

 numerous, but the protein content appears to be mainly 

 determined by that of the mother plant. By self-fertilisation 

 of selected maize the percentage of protein can be rapidly 

 increased, but apparently at the expense of total yield. 



Morphology and Anatomy. — Experiments carried out by A. W. 

 Hill upon Cyclamen {Ann. Bot.) embryos seem to place beyond 

 doubt the cotyledonary nature of the curved rudiment which, 

 when the cotyledon proper is removed, develops a normal 

 lamina. Boodle, who has studied the mode of origin of 

 adventitious leaves from the tubers of Cyclamen, finds three 

 types. Some are strictly exogenous, or if periderm has been 

 formed they arise just below the cork. In cut tubers the 

 adventitious leaves may even arise from deep-seated cortical 

 cells. 



The effect of environmental conditions on the sexuality of 

 Cannabis has been studied by Schaffner {Bot. Gaz., Mar.), 

 who finds that both carpellate and pistillate plants show 

 reversal in their growing period to the opposite sex, and 

 that their potentialities in either direction are largely influenced 

 by the environmental conditions. 



Harris, in collaboration with other investigators {Amer. 

 Jour. Bot., Feb.), has carried out an extensive study of 

 dimerous and trimerous seedlings of Phaseolus vulgaris, 

 in which the anatomical variation was studied on statistical 



