CAUSES OP THE MOTION OF JUICES. 369 



water, TFJ 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 MaVch 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 (Earsten's 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 effect, 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. (Phytopathol- 

 ogie, p. 87.) This mechanical effect 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. 



1C* 



