CORRESPONDENCE. 



Butcher's Broom. 



The Butcher's Broom, Rnscus aculeatns, flowers in March, but in the 

 years 1884, 5, 6, 7, i8go, i it was flowering freely in November in 

 Sussex and Hampshire. In November, 1888 and i88g, I was in 

 London and could not observe it. Is this an instance of.the prema- 

 ture opening of flower-buds that should lie dormant till next spring, 

 or has the plant two flowering seasons in the year ? Only a small 

 number of the plants, perhaps one in fifty, produce any fruit, and it 

 is difficult to find a bush bearing as many as a dozen berries. The 

 November flowers seldom if ever produce fruit, the November-ripening 

 berries being formed by the March flowers. Is the scarcity of fruit 

 in this country connected with the premature opening of most of the 

 flowers ? Whatever may be the reason of this double flowering 

 season, it seems to be a marked instance of the non-adaptation of a 

 plant to present climatic conditions. Clement Retd. 



TO CORRESPONDENTS. 



A II communications f 07' the Editor to be addressed to the Editorial 

 Offices, 67-69 Chancery Lane, London, W.C. 



Canker in Fruit Trees — (W. H. Shriibsole, Sheerness). — The varied and 

 often extensive malformations to which the term "canker" is applied are 

 not directly associated with any individual active agent. There is not the 

 definite relation between the disease and a certain germ which obtains, for 

 instance, in the potato-disease. The primary cause is an injury to the cambium 

 layer, resulting in cessation of growth at the point affected. The injury is often 

 inflicted at a very early age, and may be due to atmospheric causes, such as frost or 

 hailstones, which have split or bruised the tender cortex, or to piercing by an insect, 

 or some other accident. For instance, the disease often starts from the base of a 

 branch which has died or become broken off, exposing the internal tissue. 



The cambium ceases to produce wood and bark at the injured part, thus causing 

 a break in the annual ring. If only atmospheric causes have come into play the 

 sore may be small, and soon healed over by the growth of " callus " or healing-tissue 

 from the margin of the wood. Frequently, however, complications ensue. The 

 damp exposed tissue, full of nutritive sap, offers a favourable nidus for the germina- 

 tion of fungus spores. The resulting mycelium spreads through the surrounding 

 cambium living upon and destroying the cells. Every year the parasite will spread 

 further, remaining dormant through the winter as resting spores, while the efforts 

 of the plant to heal over the gradually widening wound will lead to the formation of 

 great lips of callus. The parasite often exercises a stimulating effect, causing, as in 

 the case of insect-galls, hypertrophy of the surrounding tissues. The following 

 are some of the principal works affording information on the subject : 



1. Handbuch der Pflanzenkrankheiten. By P. Sorauer. Two parts. Berlin: 

 Paul Parey, 1886. (A general text-book of plant diseases.) 



2. Lehrbuch der Baumkrankheiten. By R. Hartig. Edit. 2. Berlin ; Springer, 

 1889. (Deals with the diseases of trees.) 



3. Timber and some of its Diseases. By H. Marshall Ward. London: 

 Macmillan & Co. (Nature Series), 1889. (A small popular treatise.) 



