69 



Plant Sanitation. 



chamber before its characteristic three-tailed spores can be observed. Rim blight 

 is supposed to be caused by the joint action of the two fungi ; according to Watt and 

 Mann it spreads far more rapidly than either Gray or Brown Blight alone. A 

 careful watch should be kept for affected bushes and the diseased leaves should 

 be gathered as soon as they are observed. 



Two instances of injury following the tapping of Hevea brasiliensis are 

 worthy of note since they appear to be due in some degree to the system of tapping 

 adopted. In the first, the tree was eighteen inches in girth and Avas marked out 

 by four vertical lines into longitudinal strips, each four and a half inches wide. 

 The second girthed thirty-six inches and was similarly divided into six strips. 

 In each case alternate strips were tapped by close-set V's, so close that the lower edge 

 of one cut almost coincided with the parallel upper edge of the next ; the interven- 

 ing strips were to be tapped the following year. But on one untapped strip in 

 the first tree and two on the second, the bark separated from the wood and 

 consequently decayed. When tapping ceased there were left three strips of bark 

 couuected by thin V-shaped bars (like the coloured paper ornaments beloved of 

 suburban land ladies), and the weakening of the tension over the tapped areas 

 allowed the untapped bark to contract and split away from the wood. The 

 undamaged strips were most probably on the shady side of the trees. 



Specimens of decayed bark taken from the fork of a Hevea stem have 

 been sent in under the impression that such decay is caused by the fungus of 

 Hevea " Canker." The pieces of bark were united by a large clot of rubber, a fact 

 which suggests that, possibly by the force of the wind on one branch, the bark had 

 been ruptured at the fork ; it is not usual to find a large flow of latex in cases 

 of fungus injury, because the fungus advances slowly and dries up or destroys 

 the cell contents as it proceeds. The decay of bark in such positions is generally 

 due to the effect of rain water which constantly runs down the sloping trunks and 

 over the fork. Examples of this are common on various trees in the Peradeniya 

 Gardens ; perhaps the best are those of Duabanga moluccana to the north of the 

 cattle-sheds. 



The question of Branch Canker in tea which received much attention last 

 year has been in abeyance for some time awaiting the results of several inoculation 

 experiments with the numerous fungi which have been found on the decayed 

 branches. It is becoming more and more evident, however, that the decay which 

 sets in from a pruning cut and runs down the branch is not due to fungi in the 

 first instance, but is simply a " die-back " which should not occur on a vigorous bush. 

 Branches on which these cankers have been completely healed have been sent in 

 as examples of the effect of a properly balanced artificial manure. A recent visitor 

 declared that these specimens were the most instructive examples of tea cultivation 

 that he had seen in Ceylon. Whether the wounds on horizontal branches can 

 be explained in a similar way is still undecided ; as far as can be ascertained, no 

 Nectria has yet been found either in Ceylon or India on these cankers. 



Will correspondents please note that the letters o. h. m. s. do not secure 

 the carriage of parcels free of charge to the Royal Botanic Gardens ; and that 

 specimens of diseases should be sent to the Gardens, not to the Experiment Station. 



