458 BOTANICAL GAZETTE [JUNE 
sections. Thickness of walls was also measured with the camera 
lucida, and special note was taken in the anatomical study of the 
number and size of cells in the ring of mechanical tissue. 
Tendrils were placed under tension of different degrees by 
causing a tendril to coil about a short piece of reed supported at . 
either end by a wire, to which was attached a cord and the same 
run over a pulley, the weight desired being attached to the other 
end of the cord. Contact without tension was obtained by the 
use of a counter-balance. Unless otherwise stated, tension and 
contact: were always secured by this means. 
- When a ligature was used to secure tension, a strip of soft 
cotton flannel was wrapped about the tendril, and the string 
secured by a series of hitches only tight enough to grip the tendril 
firmly. This was found not to injure the tendril in the least, 
since it develops a soft cushion of tissue at the place of contact; 
moreover, in Passiflora a greater number of xylem cells is always 
produced at the place of contact, which tends to prevent any 
injury to the tissues. Sections taken at the place of ligaturing, 
except where too heavy weighting was introduced, showed the 
mechanical tissues to be normal, and the outside diameter often 
greater at this place than either immediately above or below. 
A series of experiments was set up to determine the effect of 
ligaturing on the development of mechanical tissues. Two sets 
of Passiflora tendrils were used for comparison; in the one set 
attachment was secured by allowing the tendril to coil about a 
support as already described, in the other a ligature was tied about 
the contact portion of the tendril, and the same amount of tension 
was applied to each. Breaking strengths of these tendrils are 
given in table I. 
These results show a slightly greater average breaking strength 
_ in the ligatured tendrils over those coiled about a support; this 
increase is evidently due to individual variation. These experi- 
ments and observations on ligaturing show clearly that the tendril 
suffers no injury whatever from this treatment. When ligatures 
were used to eliminate the contact stimulus, they were applied in 
some experiments one day, in others two days after the time when 
the tendrils were most sensitive to contact. Carnoy’s fluid (4) 
