5 2 
the shape of the leaf, the hairy growth on the margin of the leaves, 
their under side, leaf stem, and the leaf shoots, as also the pheno- 
menon already alluded to as the dimorphism of the branches.” I 
hold these data sufficiently conclusive to demonstrate that the Las 
Cascadas rubber tree is indeed the true Castilloa elastica. The 
fact that these trees produce a good yield of an excellent quality of 
rubber may well be taken as contributory evidence in the same 
direction. 
As regards the unquestionable differences of those trees from the 
C. elastica as generally described, I cannot say that I ascribe any 
importance to them. Castilloa elastica possesses such an enor- 
mously wide geographical distribution — from Lat. 6° S. to Lat. 22° 
N. — It occurs under so very greatly varying conditions of soil, eleva- 
tion humidity and temperature limits that it would be most extra- 
ordinary if it accommodated itself to all those different conditions 
without at least some morphological change. Indeed, it seems 
highly probable that some of the varying statements regarding the 
growth of Castilloa elastica in different districts may find their 
explanation in the influence upon this tree of different climatic con- 
ditions. To some extent tin's may also be true with regard to the 
various conflicting statements regarding the yield of rubber obtain- 
able from these trees. 
On this question of the amount of rubber yielded by Castilloa 
elastic i the information at our disposal from numerous sources is 
characterised by a degree of discrepancy perfectly appalling. Ac- 
cording to CROSS, a Castilloa of from 18 to 24 inches in diameter 
produces 13 lbs. of rubber annually, but he asserts that certain ex- 
ceptional trees may yield as much as 100 lbs. COLLINS observed that 
a 6 year old Castilloa possessing a diameter of 19 inches on being 
tapped in April in the dry season furnished 20 gallons of latex, 
from which 49 lbs. of rubber were obtained and he declares this 
an average yield of all trees, the tfunk of which before branching out, 
reaches a height of from 18 to 27 feet above the soil: In. Nicara- 
gua, it is found that from its sixth or seventh year, a Castilloa tree 
yields from 4 to 6 lbs. of rubber annually (Crawford), Dr. M5RRIS 
states that a Castilloa, when first tapped, should yield 16 lbs. oE 
rubber. In Mexico, it appears to be generally assumed that Cas- 
tilloa trees, when, from 4 to 5 years old, will produce an average 
vield of 6 lbs. of rubber. However the “Bureau ^Informations 
Agricoles du Mexique ” is rather more careful, giving the yield of 
the trees in question as amounting to from 4 5 ^s. ^ latex, 
corresponding to 2 lbs. 6 ozs. of rubber. 
J. H. Hart (Trinidad), states the yield of Castilloa as amount- 
incr to 2 to 6 lbs., but from quite a recent communication, I take it 
that an experimental tapping oi one of his largest trees only pro- 
duced about 14 ozs. of rubber. 
According to these above set out statements we would have to 
come to the delightful conclusion that, from its sixth or seventh 
year, Castilloa elastica will yield from 6 to 49 lbs. of rubber annu- 
ally. 
On the other hand, we' have the results of the experiments ot 
