598 



f)Ijserver found that the disease had occurred on 20 other vines, which stood 

 in depressions in the soil. 



The fact that the grape canker appears at a definite height on the vine 

 is explained by the various differences between the heat maximum and 

 minimum to which the vines, at different heights, are often exposed at the 

 time of spring frosts. 



Draining of the soil might prove the most effective method. Kohlcr 

 has already announced fa\()rat)le results in his above-mentioned works, 

 liesides this, attention should be given to the planting of hardier varieties 

 and especially the choice of suitable i)ositions (moderately moist, porous 

 and warm soil). 



It is not inconcei\able that the scab, without the action of frost, may 

 be produced by an accumulation of plastic materials, as Blankenhorn and 

 Miihlhauser beliexe they ha\ e observed as the result of too severe cutting 

 back'. It is certain that the beginnings of the swellings, occurring in tlie 

 form of medullary ray excrescences, can appear in the vines in which in 

 tlie spring the bark has been raised in places from the wood of the pre\ious 

 year. Such canker excrescences, as said above, can mature without any 

 injury from frost, just as canker-like, excrescent overgrowth edges are 

 found in luxuriantly growing pomaceous varieties. P)Ut in such cases, the 

 deep, extensive browning of the wood body is lacking. 



c. Canker on Spiraea. 



A disease, not yet described, sliowing great relation to the canker oi 

 tlie gra])e. attacks the bases of tlie stem of Spiraea opulifolia. The disease 

 seems to occur more conmionly only in regions with very cold winters. The 

 material which I had for observation came from East Prussia. 



Other wood, at least two years old, with strong annual rings shows at 

 the stem bases unusually abundant hemispherical swellings of the wood, 

 scattered, or in row's like chains of beads, or in masses. (Fig. 141 ,-/, k, 

 kk). Tlie size of these swellings varies from a few millimetres up to 1.5 

 to 2 cm. in diameter. The swellings are brown, darker than the outermost 

 Ijark layers, which they rupture, and loosened in tatters. They are often 

 cleft or depressed in the centre like a funnel and provided with thick granu- 

 lated, torn surfaces. No single bark layer can be raised, since the tissue 

 of the swelling is brittle and easily breaks off in pieces. 



In cutting away a considerable swelling, or, as one is justified in saying, 

 canker knot, it is found that lamellae or firmer material radiate out from a 

 more or less broad base. However, the lamellae neither extend through 

 the whole thickness of the canker, nor are they separated sharply from the 

 tinder-like, decayed, darker ground tissue. This itself is to be considered 

 an excrescent continuation of the last annual rinif, which becomes more 

 and more delicate toward the periphery. 



1 cf. Wurzburger Weinbaukongress. 



