MacDouGaL: Some CorRELATIONS OF LEAVES 509 
the newly formed branches were enclosed and in the winter con- 
dition. My absence from the Garden during July prevented obser- 
vations being taken during a period of four weeks, but an exami- 
nation of the plants on July 30 showed that all of the newly formed 
delaminated branches of this season had perished and that buds on 
the older branches had awakened and extended to a length some- 
thing less than the normal growth of the earlier part of the season. 
The increase in the amount of chlorophy] in the cortex may be 
considered as a further effort to meet the losses ensuing from the 
lack of the laminar portions of leaves. The non-development of 
the phellogen and the imperfect construction of the bast fibers and 
fibrovascular bundles may be ascribed in part to a lack of formative 
material and in part to the absence of the stimulation ensuing from 
the decreased transpiration stream and the material usually formed 
in the laminae. In addition, the mechanical strains and stresses 
exerted by the foliar organs undoubtedly exert some stimulative 
effect on the rigidity and pliability of the stems by the induction of 
the development of various mechanical elements. The absence of 
stimuli of this character would account in part for the imperfect 
development of the stems. 
The tests with Acer were much more restricted. The petioles 
were excised near the base and the effect upon the activity of the 
vegetative points noted. Only a single basal branch of a small 
tree was treated in this manner, and comparisons were made with 
corresponding portions of similar branches arising from the same 
part of the central stem. 
The single normal branch taken for comparison developed 
four internodes which had a diameter about thirty per cent. greater 
than the internodes of the defoliated branch. The total length of 
the four newly formed internodes amounted to 78 mm., the longest 
being the third from the base of the yearly growth, measuring 25 
mm. Eight active functional leaves were developed. (One has 
been cut away in the illustration, 6 2, A.) The newly-grown part 
of the defoliated branch measured 48 mm. and comprised seven 
internodes, the longest of which was the sixth from the base, 
measuring 8mm. The excision of the leaves had induced the de- 
velopment of one bud in the axil of the last internode of the 
Previous season. The branchlet thus formed showed two long 
