262 BOTANICAL GAZETTE [ocTOBER 
The method which gave the best results and which was generally 
used was as follows: Cross-sections of uniform thickness were 
placed in watch glasses with a little 50 per cent alcohol and two 
or three drops of alcoholic safranin. In the course of three or four 
days, all the lignified cell walls were stained a bright red, while 
other tissues remained nearly colorless. The sections were then 
either washed in water and mounted in glycerin, or washed in 96 
per cent alcohol, cleared in clove oil, and mounted in balsam. 
Since xylem forms by far the greatest part of the strengthening, 
or mechanical, tissue, more measurements were made of this than 
of the other tissues. For this purpose, exact camera drawings 
of the lignified parts were made and the area of these drawings 
determined by means of a polar planimeter. Thickness of wall 
was determined by taking the average of several measurements, 
which were made by means of an eyepiece micrometer. Relative 
size of cells was determined by counting the number in a certain 
field in the microscope or by micrometer measurements. 
In order to avoid the danger of a personal error in making the 
mechanical tests and microscopic measurements, the stems were 
numbered indiscriminately by a second person, so that the writer 
did not know which were experimental and which were control 
plants until after all tests and measurements were made and the 
results copied. 
Experimental 
COMMON LOCUST (ONE-YEAR-OLD PLANTS) _ 
In April, before the growth had begun, 14 one-year-old plants | 
were selected from a large number of sprouts. These plants were 
measured, tied securely to stakes, and weights suspended upon 
one-half of them. The cords about the stems were shifted from 
time to time to avoid constricting the stems as they increased 12 
size. More weight was placed upon the experimental plants, 
from time to time, as long as they continued to grow. In October, 
when the experiment was concluded, some of the larger stems were | 
supporting a weight of 20 kilos. : 7 
The results for this series of plants were not satisfactory 1? all 
respects. Several of the stems were broken or otherwise inju 
