38 botanical gazette. [February, 



Several theories respecting eccentric growth fail at once 

 when applied as a reason for the one-sided development of 

 the Liquidambar wing. For example, that of gravity, which 

 tends to produce a greater deposition of food material on the 

 under side of horizontal branches. The wings never start 

 from the under, but always from the upper, side of such 

 branches. Another theory is that unequal pressure of the 

 rind causes the inequality of growth of the ring, which is 

 equally inapplicable in the present case. The agency of 

 light seems a plausible theory in respect to the wings on the 

 horizontal branches, but fails to explain their appearing first 

 on one side of the young main axis. 



On the other hand, if it be regarded from the standpoint 

 of utility, as a contrivance to further the welfare of the plant, 

 the question is again extremely puzzling. The probability 

 of its serving to facilitate the interchange of gases, or affect 

 transpiration in any way, seems much less likely than in the 

 preceding instances. To those advocating the theory of 

 water absorption, by various contrivances on leaves and stem, 

 the ^rough-shape which the wings assume suggests the possi- 

 bility of their use as water reservoirs and conductors to those 

 parts of the stem where the water may be taken into the in- 

 terior. This view is mentioned rather as a fanciful sugges- 

 tion than otherwise, though both morphology and anatomy 

 go to show the possibility of the tree making this use of the 

 wing. It is just possible the suggestion is not more unrea- 

 sonable than some similar ones made in reference to various 

 appliances for making use of water. 



There is, however, another view which suggests itself, 

 and that is, the wing may be regarded as a contrivance for 

 local increase of circumference without affecting the working 

 quality of the remaining part of the periderm. By referring 

 to fig. 18 it will be seen that on a four years' stem the cir- 

 cumterence has been increased nearly one-half by the growth 

 of the divided wing, the rest of the circumference remaining 

 in the same condition as in the first season. Other branches 

 are olten nearly covered with the wing development, leaving 

 only a narrow strip of circumference in its early condition^ 

 With increasing age comes increasing demand for protection, 

 especially in case of the main axis. This is supplied by the 

 corky growth extending itself to the whole circumference, 

 while the interchange of gases is rendered possible by the 

 breaking of tissues down to the new tender-walled cells near 

 the phellogen layer. This tree is one of those described by 



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