26 



with the species which attacks junipers in the United States. In Kenya 

 Colony it is very prevalent in many of the cedar forests, and causes a vast 

 amount of loss in timber production. It attacks the heartwood of standing 

 trees, the spores gaining admission through the exposed bases of broken 

 branches and through other wounds in which the heartwood is exposed. As 

 a rule there is no outward sign of attack, the presence of the disease being 

 revealed only after the tree is felled and cut open. Sometimes, however, the 

 perennial hoof-shaped (ungulate) fructifications, woody in texture, with a 

 rusty brown spore-bearing surface (pileus.) on the under side, may be found 

 growing on the side of the tree, almost invariably at a point where a branch 

 has been broken off. When an affected tree is cut open the attack in its early 

 stages is revealed by the presence of small flecks or pockets of whitish decay- 

 ing tissue separated by sound wood. At a later stage of the attack irregular 

 hollows of considerable size are formed containing masses of brownish yellow 

 felty mycelium, and the tissues of the wood in the neighbourhood of the 

 hollows are disintegrated and permeated by the hyphse of the fungus. Some- 

 times the whole tree is hollow. Timber from affected trees may be entirely 

 worthless, and even if a certain proportion of it is sound, conversion is 

 rendered difficult, its cost is increased, and there is at the best a considerable 

 amount of wastage. 



The fungus attacks only the heartwood of trees, and it is not known to 

 gain admission otherwise than through wounds. Trees are sometimes found 

 to be hollow at the base, and it might appear therefore that the disease 

 spreads upwards from the roots, gaining admission through them by contact 

 with the roots of affected trees. I was unable to find any evidence of this 

 mode of infection, which, on the analogy of other fungi of similar habits, 

 is probably not characteristic of this fungus, though this statement requires 

 verification. In the case of hollow bases it is more probable that the fungus, 

 where present, has obtained admission through wounds caused by fire or 

 some other form of injury. Trees are more affected in some localities than 

 in others, and the presumption is that in the former case, they have been more 

 exposed to injury than in the latter. Young trees are less commonly affected 

 than trees past middle age; this naturally follows from the fact that the latter 

 contain more heartwood and have been exposed longer to the risk of attack. 



The disease is to a large extent preventible. Since the spores gain 

 admission through wounds in which the heartwood is exposed, the following 

 measures should go far towards keeping it in check : 



(1) Strict protection from fire and other injury. 



(2) The growing of cedar in close crops, preferably with the aid of 

 nurses or in suitable permanent mixtures, with the object of effecting 

 natural pruning of the branches while these are still young and have not 

 begun to form heartwood. 



(3) Periodical removal in thinnings of all stems with broken branches 

 or wounds in which the heartwood is exposed, and those actually found 

 to be attacked by the fungus. 



Further information should be collected as to the conditions under which 

 the disease is prevalent or the reverse, and as to the minimum age or size of 

 trees attacked; it may thus be possible to fix the rotation so that trees may 

 be felled before they become seriously affected. 



27. IMPORTS AND EXPORTS. The average annual imports of timber for 

 the two quinquennial periods preceding the year 1916 were as follows : 



1905-09 ... 3,079 tons valued at 13,141 



1910-15 5,292 tons valued at 25,393 



