MICRO-NUTRIENT PROBLEMS 55 



tained one-tenth of the midrib, half the rest of the leaf was per- 

 meated, but if more than one-fifth of the midrib was contained 

 in the part removed, the whole of the remainder of the leaf and 

 parts of neighbouring ones became permeated. This should be 

 avoided since neighbouring leaves can serve as a control. With 

 compound leaves, such as those of the strawberry, injection can 

 be so contrived that one leaflet becomes permeated and another 

 unaffected, while the third is partially permeated. Roach found 

 that with leaves of apple and pear injection should proceed for 

 about 10 hr. ; a response is apparent in from 7 to 10 days. 



With leaf -stalk injection the whole, instead of part only, of 

 the lamina is removed, and the leaf stalk left attached to the 

 plant is connected with narrow rubber tubing (such as tyre 

 valve tubing) to a reservoir of the solution. As a result certain 

 leaves of the plant become completely permeated, others par- 

 tially and yet others not at all; the greater the angular distance 

 of any leaf from the injected leaf stalk the less the permeation. 

 In partially permeated leaves the permeated and non-permeated 

 areas are, at any rate in the case of apple, sharply delimited, and 

 such leaves are considered by Roach to be almost ideal for 

 showing differences in colour and rate of growth of affected and 

 control areas. The method would appear to be applicable to a 

 wide range of species. 



For shoot-tip injection the tip of a shoot is removed and either 

 a small glass tube of solution is attached to the cut end of the 

 shoot with fine rubber tubing if the shoot is rigid enough to 

 support it, or the cut end of the shoot is bent over into a reservoir 

 of the solution. As a result one or more of the leaves on the shoot 

 become permeated. 



The remaining methods of injection listed by Roach are of 

 less interest from the point of view of their value for diagnostic 

 purposes, but reference may be made to the methods used by 

 Anderssen and by Storey and Leach, since these were both devised 

 in connexion with work on mineral deficiency of plants. Anders- 

 sen's method consisted in bending over the leaf and immersing 

 it in a weak solution of copper sulphate containing 0-3 p. p.m. 

 of copper. By this treatment chlorotic leaves of plum recovered 

 their normal green colour in 2 weeks, a result which afforded 

 confirmatory evidence that the pathological condition of the 



