11 



Saps and Exudations 



jH r- : _jf y OU attempt to kill most trees you usually get a copious 



blossom which does not usually seed ; it is the last effort to reproduce seed, and there 

 is no doubt that the removal of the bark, very frequently, upsets the natural 

 periodicity of the plant. The bark is the means whereby the materials in the leaves 

 are conducted from above downwards and on which the tree feeds ; if you cut that 

 away, it may become a very serious matter if done too often. 



SHOULD A FLOWERING TREE BE TAPPED? 



Mr. Smith:— Is it right to tap a tree when it is flowering ? 

 Mr. Wright:— That is a difficult question to decide as far as the yield 

 obtainable during that season is concerned. 

 Mr. Smith :— Does it affect the seed ? 



Mr. Wright :— Any treatment Avill affect the seed in some way or other 

 if it is severe enough. The effect of tapping upon seed is a rather complicated 

 one. It is possible to imagine, should you tap trees, you may induce favourable 

 characteristics in the seed ; if you train a tree up to give plenty of bark and 

 produce distended latex tubes, it may lead to a similar formation in the seed 

 and it may be an advantage to have seeds from tapped trees. But on the 

 other hand if the ordinary tapping operation is conducted in a manner which 

 threatens the life of the tree, it may lead to deterioration of the seed. It brings 

 up the whole subject of whether you can induce characters which can be trans- 

 mitted by seed, a difficult question to settle off-hand. 



Mr. Harries :— During February and March I noticed flowers on 4-year-old 

 trees, but they never came to anything. They all fell x)ff, 



Mr. Wright :— I think trees have been known to flower and seed when 

 24 years old in the Straits ; when they are 4 to 5 years old in Ceylon, flowering 

 frequently occurs. 



Mr. Harries :— But why February and March ? 



Mr. Wright :— That is to some extent irregular if it occurs in February 

 in Ceylon. The flowers usually come out a month or so after the new leaves 

 on a young tree. 



Mr. Harries :— But this was a 4-year-old tree. 



Mr. Weatherall :— Are you sure it was a rubber tree? (Laughter.) 

 increase of girth and bark. 



Mr. B. H. Jenktns :— Does this increase in the circumference of a tree 

 lead to an increased thickness in the bark of the younger tree ? It is a physical 

 impossibility to tap a young tree. The bark is not thick enough and you go 

 into the cambium every time. What I want to know is whether, by increasing 

 the girth of the tree as you suggest, you increase the thickness of the bark ? 



Mr. Wright : — It is rather a complicated and technical point. The cambium 

 produces wood internally and bark externally ; these tissues are formed in a 

 regular manner, so many wood cells being produced for a definite number of bark 

 cells. If the cambium produces more wood, it must necessarily produce more 

 bark, because the two tissues are produced in definite proportions. That is why — 

 in valuing different estates — you can approximately judge the thickness of the 

 bark by examining the rings in the wood of the stem. The broader the rings 

 of growth in the wood, the thicker the bark. Any increase in growth almost 

 invariably means an increase in wood and bark ; it is unusual to get one growth 

 without the other. 



Mr. Jenkyns :— In a pruned tree of four years old, you would have a 

 sufficiently great thickness of bark to get a cut into it, while in an unpruned tree 

 of the same age you probably would not. 



