MECHANICAL tl'FECTS OF OSMOSE OK THE PLAHT. 369 



water, W, which is put under pressure by pouring mercury 

 into the upper extremity of the syphon-tube. Horse- 

 chestnut and grape twigs cut in February and March and 

 thus treated,— the pressure of mercury being equal to 6-8 

 inches above the level, M, — after 4-6 weeks, unfolded their 

 buds with normal vigor, while twigs similarly circum- 

 stanced but without pressure opened 4-8 days later and 

 with less appearance of strength. 



Fr. Schulze {Karstenh Bot. TTnters., Berlin, II, 143) 

 found that cuttings of twigs in the leaf, from the horse- 

 chestnut, locust, willow and rose, subjected to hydrostatic 

 pressure in the same way, remained longer turgescent and 

 advanced much farther in development of leaves and flow- 

 ers than twigs simply immersed in water. 



The amount of water in the soil influences both the ab- 

 solute and relative quantity of this ingredient in the plant. 

 It is a common observation that rainy spring weather 

 causes a rank growth of grass and straw, while the 

 yield of hay and grain is not correspondingly increased. 

 The root-action must operate with greater eflect, other 

 things being equal, in a nearly saturated soil than in one 

 which is less moist, and the young cells of a plant situated 

 in the former must be subjected to greater internal stress 

 than those of one growing in the latter — must, as a con- 

 sequence, attain greater dimensions. It is not uncommon 

 to find fleshy roots, especially radishes which have grown 

 in hot-beds, split apart lengthwise, and Hallier mentions 

 the fact of a sound root of petersilia splitting open after 

 immersion in water for two or three days. (PhytopathoJr 

 ogie, p. 87.) This mechanical eflect is indeed commonly 

 conjoined with others resulting from abundant nutrition, 

 but increased bulk of a plant without corresponding in- 

 crease of dry matter is doubtless in great part the conse- 

 quence of large supplies of water to the roots and its vig- 

 orous osmose into the expanding plant. 



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