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JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



other parasitic plants, grows only upon its particular host — the 

 Larch tree — and that should the spores light on any other plant 

 they cannot grow and will do no harm. 



There is one point about the Larch canker which is of great 

 importance with regard to the cure and prevention of the disease, 

 and that is that — as far as observation has gone — the disease 

 does not attack trees of more than two or three years old, and it 

 appears that when the tree has formed a sufficient layer of bark 

 the germinating spore cannot find an entrance, and, therefore, 

 all young trees of four or five years old which are absolutely 

 free from disease may be considered to have passed the critical 

 stage. It must, however, be remembered that there are always 

 young branches in a healthy tree, and that these, with their soft 

 cortex, are equally liable with the stems of young trees— though 

 in the case of diseased branches pruning can easily be employed 

 without depreciating the value of the timber. It seems, how- 

 ever, that the tree and its branches, having got its coat of 

 bark, can resist the germinating spore if it preserves its cortex 

 unbroken, but should the bark be taken off, even from a small 

 portion, a spore may be washed into the crevice and the disease 

 propagated. 



The ordinary forester cannot, perhaps, be expected to study 

 the life-history of such a minute plant as Dasyscypha Will- 

 kommii, but even with the help of a magnifying glass he 

 should be able to recognise sufficient of the external structure of 

 the parasite to satisfy himself of its true nature, and also to be 

 able at the outset to detect it, and take such steps as he may 

 deem best to circumvent it. 



With regard to methods of prevention and cure, much 

 might be written about the former, and much has been written 

 by many eminently practical men on the subject of procuring 

 good seeds, so that the seeding plants should not be already 

 tainted with the disease. Until, however, it is conclusively 

 proved that the seeds contain the spores or mycelium of the 

 fungus, it cannot be positively stated that the seeds contain the 

 disease, or that "unhealthy seedlings" are the cause of its 

 appearance ; and as all the trees examined by both German and 

 English workers show in section that they have been attacked 

 after they have grown some little time, to cast the blame upon 

 the seedlings seems hardly fair. There is no doubt that 

 crowded plantations favour to no little extent the rapid spread 



