Branner.} 480 [April 18, 
angle with the surface of the apex, and are more nearly erect. But when, 
in the course of time, the fronds which are now the highest, come to be 
the lowest, the angle they make with the periphery will have been much 
increased by the lateral growth of the trunk, which will bring the fronds 
out at shorter radii, and the result will be a more decided drooping of the 
lower fronds. In this arrangement upon the growing part is a provision 
for the weakness of the young fronds, which could not sustain their own 
weight if the angle made with the trunk were a larger one. I have already 
explained that the shorter radius at the surface, as seen in the lower fronds, 
ig due to the lateral growth being greater than the longitudinal, and, of 
course, takes place as the fronds come to be the lowest in the crown. 
T have also stated that in palms having perfectly cylindrical stems, the 
fibro-vascular bundles average the same size from the base to the upper 
end of the full grown part. They vary however in each division, reach- 
ing their gréatest development within the trunk just where they curve 
outwards to connect with the external growth, and beyond this to a dis- 
tance in the petiole varying with the length and weight of the normal 
frond. The variation in size appears to be due to the purpose which the 
bundle serves at the given part. In those palms which have long and 
heavy fronds, the bundles are greatly developed near the base, and in 
addition, they assume structural forms capable of adding to their strength 
in the manner needed by the tree, while in those having short and light 
fronds there is comparatively little development of the bundles at the bases 
of the petioles.* The frond of Raphia tadigera (Jupatg) is noted for its 
great length and weight.+ In this palm the fibro-vascular bundles are 
cylindrical, or reach their greatest lateral development just at the june- 
ture of the frond with the stem, and are flattened laterally in the base of the 
petiole, the upper edge being the thicker. This shape gives them about three 
times the strength they would have in the ordinary cylindrical shape, for 
supporting a weight applied as it is in this part of the petiole. There is 
another structural peculiarity about these bundles in Raphia tadigera, 
which I have not sufficiently investigated. When a frond dies, it breaks 
oft just beyond the enlarged part of these bundles, and in time the broken 
petiole that remains fast to the trunk decays, leaving the larger fibro-vas- 
cwar bundles exposed. In this condition, one might expect to find 
them bent downwards by the strain of great weight sustained by them 
from the beginning until they became rigid. But so far are they from 
being warped downwards, they ar not even straight, but bend back 
* Jupatg, pataud, murumurt, urucurg and uauasst all have large fronds, and 
proportionately large fibro- vascular bundles in the bases of the petioles. Assat, 
the marajds, the paxitibas and mucajdés have small fronds, and small bundles in 
the bases of their petioles. 
+ I have measured fronds of this palm that were fifteen metres long. Wallace 
says he has seen them fifty feet long, V. Wallace’s “Palms of the Amazon,” 
p. 43. 
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