ANATOMY OF (iTAVr i.i:. 177 



appears therefore not to prohibit rubber secretion, but to 

 slow it down. At the same time, profound anatomical 

 changes are induced which may effect the total amount, of 

 possible secretion. To what extent these changes may be 

 oftset by later reactions it remains for time to indicate. 



Secretion of rubber cuid size of plant. Ross states that 

 the rubber producing stuffs are not extensively produced, and 

 only very slowly at first, in small plants. P^or this reason it 

 d<;es not pay to w^ork plants less than ten years old. 



The statement is one very much in vogue in Mexico. I 

 have heard it said frequently that small plants contain no 

 rubber. The amount of rubber varies in different plants 

 from different habitats, as would be expected from tlie facts 

 above pointed out, but that there is such a difference be- 

 tween large and small plants from the same habitat as one 

 must be led to infer from the statements made, I find to be 

 open to question. I have examined microscopically, and by 

 mechanical extraction seedlings of all ages, from one year 

 up. and it is very difficult to believe that the relative amount 

 of rubber is as little as is supposed. That it would not pay 

 to gather small plants is true for reasons of economy in 

 handling alone, disregarding the far more important reason 

 of reforestation. 



Resin canals. Ross describes correctly the occurrence 

 and distribution of the resin canals in the stem, where, both 

 in the pith and cortex, at the growing apex, they arise very 

 early by splitting, and usually stand in relation to the 

 bundles. Those of the pith are and usually remain cylin- 

 drical, while those of the cortex soon become compressed at 

 right angles to the radii. Canals are found also in the 

 leaves, on both sides of the stronger bundles, and on the wood 

 side only of the weaker ones. The lining cells have dense 

 contents. 



In addition to these observations, T have found certain 

 peculiarities which should be noted. Pith canals do not occur 

 in the epicotyledonary stem for the first few intcrnodes, nor 



