408 HOW CROPS GROW. 



extremity of the syphon-tube. Horse-chestnut and grape 

 twigs cut in February aud March and thus treated — the 

 pressure ol mercury being equal to six to eight incbes 

 aboTe the level, Jf— after four to six weeks, unfolded 

 their buds with normal vigor, while twigs similarly cir- 

 cumstanced but without pressure opened foUr to eight 

 days later and with less appearance of strength. 



Fr. Schulz {Earsten's Bot. Unters., Berlin, II, 143) 

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

 chestnut, locust, willow and rose, subjected to hydro- 

 static pressure in the same way, remained longer turges- 

 cent and advanced much further in development of 

 leaves and flowers than twigs simply immersed in water. 



I'he amount of water in the soil influences both the 

 absolute aud relative quantity of this ingredient in the 

 plant. It is a common obs'ervation that rainy spring 

 weather causes a rank growth of grass and straw, while 

 the yield of hay and grain is not corrfespcndingly in- 

 creased. 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 consequence, attain greater dimen- 

 sions. It is not uncommon to find fleshy roots, espec- 

 ially 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. {Phytopathologie, p. 87.) This 

 mechanical effect is indeed commonly conjoined with 

 others resulting from abundant nutrition, but increased 

 bulk of a plant without corresponding increase of dry 

 matter is doubtless in great part the consequence of large 

 supplies of water to the roots and its vigorous osmose 

 into the expanding plant. 



