284 Report of the Botanical Department of the 



above. In two instances where measurements were taken the com- 

 ponent parts of the crotches had separated about 2 cm., which seems 

 to indicate that there had also been a longitudinal contraction of the 

 outer portions of the trunks, thus resulting in an outward bending 

 of the branches. The bark, however, had not separated or loosened 

 from the wood along the clefts. 



Many shade trees in the city of Madison, including maple, oak, 

 catalpa, linden, etc., also had their trunks cleft open during the first 

 week of January. Frequently a long cleft extended from near the 

 ground up as high as 2 meters, and one or more shorter ones from 

 near the ground up about 5 dm. or less. The longer clefts went at 

 least as far in as the center of the trunk. No bark had been loosened. 



Changes in circumference of cleft trunks due to rise of temperature. — 

 Some measurements were taken on linden and catalpa trees on Jan- 

 uary 6 when the thermometer stood at — 28.3° C, which are recorded 

 in the table below. In this case, also, errors that may have arisen due 

 to the contraction of the steel tape-measure would result in giving 

 higher values to the measurements at low temperatures and thus 

 give slightly lower percentages of increase in the circumference when 

 compared with those taken at higher temperatures. The measure- 

 ments were made at marked points on the trunks and also included 

 the width of the clefts. When the second measurement was made 

 the clefts had all closed tightly. The change in circumference that 



Table II. — Measurements on Shade Trees in Madison which Were Cleft 



During the Winter of 1911-12 



these tree trunks underwent between January 6 and April 6 was 

 therefore greater than is shown by the measurements on which the 

 first column of percentages is based. After deducing the width of 

 the clefts from the measurements made on January 6, the percentages 

 of increase in the circumferences are appreciably higher, as shown 

 in the last vertical column. 



