96 DISEASE IN I'LANTS. 



conditions do not become unfavourable, an in- 

 creased root-supply may by its larger absorbing 

 area gradually establish the former state of equili- 

 brium of functions. But this at the expense of 

 the plant, which is smaller, has fewer leaves and 

 narrower water channels, etc., than a plant not 

 thus checked, and it may take a long time to 

 make up for the loss of time and stature thus 

 incurred. Indeed if the plant is an annual no 

 recovery at all may occur, the reserves passing 

 into fruit and seeds instead of slowly supplying 

 the roots as described. 



If it be asked, can such a condition of affairs as 

 that described really occur, we have only to think 

 of a transplanted specimen with its roots maimed 

 and put into unsuitable soil, or of plants in the 

 open with feeding roots gnawed by an insect, etc., 

 or of a tree hitherto in equilibrium with its fellows 

 in a plantation suddenly set free by thinning and 

 so forth. 



Now take the case where the roots are main- 

 taining their maximum functional activity, but the 

 leaves owing to want of light, too much moisture 

 or too low a temperature of the air are function- 

 ally depressed. Here we get a state of over- 

 saturation with water set up, the tissues are turgid 

 to bursting point, what supplies do traverse the 

 sieve-tubes, cortex, etc., do so slowly and are 

 excessively diluted, and the cambium again forms 

 less wood, but the lumina of the vessels are larger 

 and the Hgnification less complete. Growth in 

 length is excessive, but more leaves are formed. 



