Undamaged branches are with difficulty infected by the parasite, but it is 

 easy, even by very slight wounds and artificial infection, if only the wounds be 

 numerous, to obtain great quantities of gum. This circumstance explains why nursery 

 men dread wounds in the trunks and branches of stone-fruit trees. 



In the green shoots, especially of the peach, the formation of anthocyan is ob- 

 served in the enfeebled tissue around the wounds infected with Coryncum when 

 exposed to sunlight '). 



The supposition that secretion products of the parasitic caterpillar or the Fun- 

 gus could be the direct cause of the stimulus, is contrary to the positively existing 

 relation between mechanical wounding and gummosis. 



Gum canals in the fruitflesh of almond and peachalmond. 



To the preceding facts, long since stated, I wish to add the following. 



Already in my first paper of 1883 I called attention to the circumstance, that 

 in the fruit-flesh of the peachalmond, and as I may add now, a'.so in that of the 

 almond itself, there is a system of gum canals, precisely corresponding to that of the 

 vascular bundels. Of these the phloem bundles are converted into gum canals by 

 cytolysis, either entirely or with the exception of the outer protophloem; the gum 

 canal (gp Fig. 2 and 3) thus, is a'ways immediately contiguous to the woody 

 bundle .r/. 



The presence of gum in the canals of the fruit is easily shown. In August or 

 September the summit of a peachalmond fruit is cut off and the fruit, or the branch 

 with the fruit, is placed in water. After some moments all over the section droplets 

 of gum are seen evidently issuing from the vascular bundles. As these bundles are 

 distributed through the fruit-flesh, running longitudinally and transversely, and are 

 partly reticulated, the number of droplets is very great and they are of different 

 size. In particular near the stone they are big. If in August the gum is allowed 

 to flow out in cold water it dissolves completely or nearly so. In September the 

 dissolving is no more complete. By drying the gum, its solubility in cold water 

 gets almost lost, but it continues in hot water. 



From lateral incisions also much gum flows out. In Fig. i the drops are repre- 

 sented after drying, followed by swelling up in cold water. 



Although this gum does not only consist of dissolved wall material but also 

 of cell contents, the microscope can only detect fine granules, evidently correspon- 

 ding to the microsomes of the protoplasm, which are not dissolved during the cyto- 

 lysis I could not find back the cell nuclei in the gum, but in the cells of the not yet 

 cytolised phloem bundles, they are neither perceptible. As under normal circum- 

 stances the gum does not flow out, its volume must be about as great as that of the 

 phloem bundles which are cytolised. It is, however, certain that the capability of 

 the gum to swell up by imbibition is much greater than that of the cell-tissue which 

 gave rise to its formation. It seems thus certain that imbibition with sufficient access 



*) The apperance of anthocyan in the light is commonK' a token of diminished 

 vitality and often a consequence of necrobiose in the adjoining cells. Hence, wounds, 

 poisons and parasitism cause anthocyan production in the most different plants. 



