368 BOTANICAL GAZETTE [JUNE 
sections of the tension-plant stem above and below the place of attach- 
ment of the cord, to note any differences in anatomical structure in 
the two regions. 
Helianthus annuus (greenhouse cultures) 
Ten plants of Helianthus annuus that had grown in the green- 
house for a month were weighted on November 4 with 50%". On the 
third day following, the weight was increased to 100%, and on the 
tenth to 200%. At this time the attachments were changed to a 
place above the original one. This, as has been mentioned above, 
was for the purpose of guarding against injury due tothe cord. Addi- 
tional weights were added at various times, until in this set of experi- 
ments the final amount reached 600%" on November 23. 
At this time the weights were removed from five plants and the 
stems placed in 50 per cent. alcohol. Five plants that had grown 
under similar conditions, except that they had not been subjected to 
tension, were also gathered to serve as controls. These controls had 
been chosen at the beginning of the experiment and were closely 
watched throughout the time of experimentation in order that all 
conditions other than tension should be the same. 
Cross-sections of the normal stem of Helianthus annuus of this age, 
at a height of 7°™ from the ground, do not show a completely closed 
xylem ring. The bundles are separate and are of various sizes. 
The secondary xylem is beginning to form. 
Sections forjmicroscopical study were made at a place 7°™ above 
the first lateral root in both tension and normal plants. The place 
of attachment of the cord-on the tension plant was some distance 
above this, so the sections were within the region of tension. Careful 
observations:by two persons, working independently, did not disclose 
any appreciable difference between tension and normal plants. 
Other sections were then made in the tension stem above and 
below the attachment. No appreciable differences are detected when 
sections in the tension region are compared with sections on the same 
plant out of the region of tension. 
As a general result of observations of the first five ae we may 
say that tension exerted upon the stem along its longitudinal axis did 
not call forth a self-regulatory development of mechanical tissue. 
