286 BOTANICAL GAZETTE [apeil 



that the double leaf -trace ^Ms neither more nor less than an early dichotomy of 

 the vascular system of the leaf/' This persistent dichotomy of the leaf-trace, 

 long after dichotomy has disappeared from the leaf, is used to explain the irregular 

 dichotomy of the leaves of Cycadofilices, the dichotomy of the early leaves of 

 modem ferns, the splitting of cotyledons in polycotyledony; and "it finds its 

 latest expression in the 'double bundle' of the cotyledons of angiosperms.'* 

 This view certainly helps to connect the angiosperms with the same old fern stock, 

 that gave rise to the g}'mnosperms.— J. M. C. 



Effect of electricity.— A very concise summary of the work previously pub- 

 lished upon the effect of electricity on the growth and development of plants 

 IS furnished by Priestley^^^ as the preface to a brief account of some recent 



MAN 



The current used was of high tension, distributed by overhead wires from which 

 depended metallic points. In general the results show a very decided increase in 

 the quantity, or quality, or earliness of the crop. Thus year-old strawberries 

 showed 80 per cent, increase, Canadian Red Fife wheat 39 per cent. The elec- 

 trified wheat produced a better baking flour and consequently sold at 7 . 5 per cent, 

 higher prices. Electrified beets not only showed S3 per cent, increase in the crop, 

 but contained over 14 per cent, more sugar. Currents traversing the earth pro- 

 duced occasionally increase in rate of growth, but often had no definite effect. 

 The physiological action of the current is not clear. Priestley rejects Pollacci's 

 view that it enables the green plant to elaborate starch in the dark.^C. R. "B. 



A theory of photosynthesis.— Gibson outlines" thus a photoelectric theor)' of 

 photosynthesis, which he is to elaborate later in cooperation with two coUeagues: 

 The light rays absorbed by chlorophyll are transformed by it into electric energ)' 

 which effects the decomposition of HXO3, with the concomitant formation of 

 an aldehyde and the evolution of oxygen. He finds a small quantity of formalde- 

 hyde present, as shown by the test of :Mulliken, Brown, and French, in ail 

 actively photosynthetic tissues, the amount being definitely related to the illumina- 

 tion. The maximum decomposition of CO, occurs in light equal to one-quarter 

 direct sunhght. H.COH may be synthesized from CO, in the presence of water 

 by a silent electric discharge, as Loeb has shown; and this Gibson confirms 

 Electric discharges of sufficient intensity have already been found in adequatelj 

 ' " ■ ated green tissues, and the light rays absorbed by chlorophyll are the ones 

 which produce these currents. He promises in the forthcoming paper to connect 



formaldehyde with carbonic acid by a photolytic method which is above suspicion. 

 C R. B. 



illu 



mm 



■ 



"Priestley, J. H., The effect of electricity upon plants. Proc. Bristol Nats. 

 Soc.IV. 1:192-203. 1907. ^ ^ ^ 



" Gibson, R. J. Harvey, A photoelectric theory of photosynthesis. Annals of 

 Botany 22:117-120. 1908. 



