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STUDIES IN PLANT REGENERATION 197 
disregarded. On the whole, however, the aim has been to separate 
such cases of pure regeneration from those which ought to be in- 
terpreted under the broader head of correlation. 
The work was started at the propagating houses of the New 
York Botanical Garden three years ago, and has been in progress 
since. Unless a statement to the contrary is made, the experimental 
material which belonged almost exclusively to the higher plants, was 
placed in the cutting-frame in the experimental house and observed 
at short intervals. This frame is of the usual type, containing 
pure sand to a depth of about 6 inches, and covered by a partly 
whitewashed glass top. It may be added that in numerous in- 
stances the cuttings were tried, also, in other environments — 
saturated air, sphagnum, sawdust, charcoal, cotton, and water. 
But in all of these, the parts decayed with far greater rapidity 
than in the sand, and few positive results were obtained under 
other cultural conditions. 
The writer desires to acknowledge indebtedness to Dr. D. T. 
MacDougal under whose direction and encouragement the work 
has been carried on, to Professor H. M. Richards for many helpful 
suggestions, and to Professor W. J. Gies for assistance on the 
chemical side of the experiments. Thanks are due also to the 
staff of the New York Botanical Garden, who have throughout 
provided every facility in their power for the successful completion 
of the work. 
Various questions presented themselves for solution at the very 
outset of the work. To decide whether every budless part of the 
plant is equally capable of regeneration, the separate plant organs 
have been used as cuttings, and their behavior is described under 
the heads of roots, stems, leaves, inflorescences, and fruits. The 
question as to the rigidity of the polarity manifested by such pieces 
has been considered with the cases in which any irregularity has 
occurred. Ina similar manner, the effect of external conditions 
has been treated both in connection with the special instances and 
as a general subject in the discussion following the experiments. 
With the object of ascertaining whether food is to be regarded as 
a necessary factor in regeneration, or whether the parts can, as has 
been stated, regenerate even under conditions of starvation, a further 
