58 PREVIOUS INVESTIGATIONS UPON PLANTS 



and Mimosa fiidica. He found that the various plant tissues ab- 

 sorbed the rays differently, so that X ray photographs may be taken 

 which disclose certain details of internal structure, such as vascular 

 bundles. 



Maldiney and Thouvenin"*' succeeded in accelerating the germi- 

 nation of seeds of Convolvulus aj'vensis, Lepidiuni sativum^ and 

 Panicum rniUaceum by exposing them to the action of X rays. From 

 the fact that these seedlings as they came from the seeds were yellow 

 as usual, the authors conclude that the rays are without influence on 

 the formation of chlorophyll. 



Tolomei'^^ states that Rontgen rays act upon plants like light. 

 Under their influence the leaves of Philotria canadensis^ in water 

 containing COj, give off bubbles of gas as in sunlight. Like light 

 also, the rays retard the absorption of oxygen by Mycodernia aceti, 

 and also the production of COj by beer-yeast. 



By exposing seeds for about an hour daily for several days to X 

 rays, Wolfenden and Forbes^* induced an acceleration of germi- 

 nation, and two years later (1902) Seckt^® published the results of 

 his studies on the influence of X rays on the plant organism. He 

 found, as did Lopriore, that the rays have a decided accelerating 

 influence upon the protoplasmic streaming in hairs of Cucurhita 

 Pepo, Tradescantia virginiana, and 7 . Sclloi. Seckt remarks that 

 this effect may be similar to that called forth by poison or by wound 

 stimulus, by which the organism is stimulated to an abnormally 

 aggravated vital activity. Spirogyra-ceWs were plasmolyzed at a 

 distance of 10-12 cm. from the X ray tube, but were indifferent to 

 the rays at greater distances. Increased turgor could also be called 

 forth by the rays. The guard cells of the stomata of Tradescantia 

 Selloi, and the pulvini of Mimosa and of Oxalis, under the influence 

 of the rays undergo an increase of cell-pressure which may have its 

 cause in a peculiar influence upon the protoplasm of the cells. 



The latest studies of the effects of Rontgen rays on plants are 

 those of Koernicke ^^' ^'^' ^^ In his first paper (1904) he announced that 

 the immediate effect of exposure is an acceleration of growth, an 

 effect similar to that which Townsend ^" found to occur in plants 

 after a slight wounding. Finally, however, growth was retarded. 

 The time intervening between exposure and the decrease in the rate 

 of growth varies with the plant and its physiological condition at the 

 time it was exposed. Brassica napus, for example, is especially 



