Cuar. LY, PASSIFLORACE. 153 
Paullinia. It was not in flower, yet bore long forked 
tendrils. So that, Paullinia, with respect to its tendrils, 
: appears to bear the same relation to Cardiospermum 
that Cissus does to Vitis. 
PasstrLorace#.—After reading the discussion and 
facts given by Mohl (p. 47) on the nature of the 
tendrils in this family, no one can doubt that they are 
modified flower-peduncles. The tendrils and the 
flower-peduncles rise close side by side; and my son, 
William E. Darwin, made sketches for me of their 
earliest state of development in the hybrid P. floribunda. 
The two organs appear at first as asingle papilla which 
gradually divides; so that the tendril appears to be a 
modified branch of the flower-peduncle. My son found 
one very young tendril surmounted by traces of floral 
organs, exactly like those on the summit of the true 
flower-peduncle at the same early age. 
Passiflora gracilis—This well-named, elegant, annual 
species differs from the other members of the group 
observed by me, in the young internodes having the 
power of revolving. It exceeds all the other climbing 
plants which I have examined, in the rapidity of its 
movements, and all tendril-bearers in the sensitiveness 
of the tendrils. The internode which carries the upper 
active tendril and which likewise carries one or two 
younger immature internodes, made three revolutions, 
following the sun, at an average rate of 1 hr. 4m.; it 
then made, the day becoming very hot, three other 
revolutions at an average rate of between 57 and 
58m.; so that the average of all six revolutions was 
