INJURIES INDUCED BY PLANTS 203 



infected wounds on the stem, takes the form of a white-rot. 

 The colour is yellowish ashy grey, alternating with stripes of a 

 pale brown colour, which generally persist longest in the 

 medullary rays. In the later stages of decomposition snow-white 

 masses of felted mycelium occur where a zone of spring wood 

 is much decayed. 



The peculiarity of the action of the ferment consists in the 

 inner layers of the cell-walls swelling up into a gelatinous mass, 

 without being converted into cellulose, before they are completely 

 dissolved ; the middle lamellae being the last to disappear. 



THELEPHORA PERDIX l * 



A form of disease which is very common in the oak throughout 

 the whole of Germany is known as " partridge wood," on account 

 of the peculiar discoloration which it induces in the wood, and 

 which reminds one of the white-speckled feathers met with on 

 certain parts of the body of the partridge. At first the diseased 

 wood assumes a deep red brown colour, and then white blotches 

 on a dark ground make their appearance which stand in a certain 

 relationship to the large medullary rays. These blotches after- 

 wards become transformed into sharply defined cavities with a 

 white lining. As the cavities, which are separated from each 

 other by firm brown wood partitions, increase in size, the wood 

 looks as though it had been attacked by ants, and, as a matter 

 of fact, the symptoms are often mistaken for the work of these 

 creatures. It is to be noted that each cavity usually remains 

 distinct until the stage of complete decomposition is reached. 

 In the wood of the oak the mycelium first induces the contents 

 of the parenchymatous organs to become brown. Gradually 

 proceeding inwards, the starch-grains fail to give a blue reaction 

 with iodine, colourless granules persisting for some time in the 

 central cells of the medullary rays, until they also are at last 

 destroyed (Fig. 126). 



Where the white blotches make their appearance, as also in 

 the partitions of the white cavities, all the organs are converted 

 into cellulose, and the middle lamellae being dissolved the 



1 R. Hartig, Zersetzftngserscheinungen, pp. 103 et seq. 

 * [I do not know this as British, but a specimen of diseased wood sent 

 from India was marked in exactly the way Hartig describes. ED.] 



