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EXPERIMENTS WITH RUBBER SEEDS. 



The Effect of Tapping on Seeds. 

 Seeds from Tapped Trees Better Germinators. 



A circular has been issued by Mr. H. F. Macmillan, the Peradeniya 

 Curator, and Mr. T. Petch, Government Mycologist, giving the results 

 of experiments carried out as to the weight and germinative capacity 

 of rubber seed. The circular says : — 



In order to obtain some reliable data as to the weight of Hevea 

 seed, its loss of weight and germinative capacity on keeping, and how 

 far the latter might be deduced from the separation of the cotyledons, 



a series of germination tests was instituted The seed at Peradeniya 



was collected from (A) a group of trees, about twenty years old, which 

 have never been tapped, and (B) a group of trees, about thirty 

 years old, which were tapped regularly in 1905 (when 29 lb., of dry 

 rubber were taken from eight trees in three months), occasionally in 

 1906, and not at all in 1907. Presumably A are the descendants of 

 B ; if not, both groups are descended from the Henaratgoda trees. 

 1,000 seeds were collected from each group. Each thousand was divid- 

 ed into ten lots of 100, which were weighed separately. One lot 

 from each thousand was planted on September 14th; on September 

 21st the remaining eighteen lots were re-weighed, and one more from 

 each thousand was planted ; and the process was repeated each week 

 until all were planted. Planting the seed is a departure from the usual 

 method of testing germination, but it was adopted in this case in order 

 to avoid the attacks of fungi, insects, rats, squirrels, &g. As far as 

 possible, the treatment, i.e., depth and kind of soil, amount of w T ater, 

 &c, was the same for all. 



The tables give the weights fin grams) of 100 seeds on the 

 date of collection and at each subsequent re-weighing. For example, 

 lot 4 consists of 100 seeds, weighing 394 grams when collected on 

 September 16th ; left in open dishes in the laboratory, they dried to 

 3,695 grams on September 21st, 341 grams on September 28th, and 

 3,325 grams on October 5th, they were planted in October 5th. It 

 was found that when they were kept in tall glass cylinders they turned 

 mouldly in a few days. Lots 3 to 7 were collected and weighed on 

 September 16th, and lots 8 to 10 on September 18th. It was impossi- 

 ble to gather 1,000 seeds from these eight trees on the same day. Lot 

 10 was sacrificed for another object after six weeks' drying, as it was 

 obvious that nothing would result from a germination test. It will be 

 seen that the seeds lose weight rapidly during the first fortnight, and 

 then more gradually till about the sixth week. After six weeks their 

 weight is approximately constant at Peradeniya, but, as will be seen later, 

 further drying occurs if they are transferred to a drier atmosphere. 

 The loss of weight in lot 7 after about six weeks' exposure is 16.6 per 

 cent.; in lot 8, 18.8 per cent.; in lot 9, 18.6 per cent.; and in lot 10, 16.5 

 per cent ; or an average loss of 17.6 per cent. This loss is practically 

 all water, which condenses on the sides when the seeds are kept in 

 glass cylinders, 



