42 The Botanical Gazette. [February, 
trifolia, and Anemonella thalictroides. Many of these roots 
which were sectioned were less than .5™" in diameter. Sec- 
tioning such roots met with many failures, especially in get 
ting good longisections of the tip. One series of transections 
of a root the diameter of which could not have been over 
.25™" was obtained, which showed the bundle structure fairly 
well. Careful camera lucida drawings were made of the 
transections of most of the roots, and these with the sections of 
the roots themselves were studied in making my comparisons. 
All of these drawings could not be embodied in this thesis, 
but many of them will be found on the plates. In the study 
of the meristem structure rough drawings were made of most 
of the tips, then comparisons were made, and but one detailed 
drawing was made for each type of structure. 
III. General structure. 
As to the general histological structure, especially as to the 
difference between old and young roots, I should make two 
general classes of the plants of Ranunculacez, first, those not 
showing decided secondary change in older roots, and second, 
those presenting certain modifications from the primary struc | 
ture in the older roots; in the second class there are two 
different modifications of the primary structure, thus making 
three classes. ‘ 
The first class includes those plants in which the original 
radial structure persists in the older roots, that is secondaty 
growth produces but little change in the plan of root struct- 
ure. The cortex may become less compact by the disappea™ 
ance of cells, and the xylem may increase in the number of 
its.rays, and its vessels in the number and thickness of thet 
walls, but the primary radial structure is still evident. | 
especially good representatives of this class I would name the 
the oldest roots showed in the bundle area simply an inc 
Is in 1 
in the number of the xylem vessels, and in the cortex If 
lar air spaces occurred through the disappearance of cel 
certain areas or the tearing apart of the cells through 798 
growth, but the plan of structure was still the same as 17 hy ] 
younger roots, this being a triad or tetrad radial bundle.“ 
