88 
FRANK C. GATES 
where no aerenchyma was produced by Sesbania, no clinging roots 
were present on the Merremia. These roots closely covered the 
aerenchymatous surface but did not seem to penetrate it. 
Lack of sufficient air in the lower part of the stem and in the roots 
was obvious. The smaller size and number of the vessels in the 
lower part, the simpler structure as well as the smaller amount of 
Fig. 2. A piece of the stem of Merremia gemella from near the center of the 
swamp. The upper and larger part was not submerged, while the lower and thinner 
part was covered with warm water. Los Banos, P. I. October 31, 19 14. 
starch present in the lower part of the stem showed that the conduction 
of the food downwards was also affected by the continued submergence 
of the stem in the warm water. The results were somewhat similar to 
girdling in that the phloem was very much congested in the upper part 
of the stem. 
If the roots developing from the stem had penetrated the supporting 
host, a first stage in the development of parasitism would have been 
apparent, but such was not the case. 
Of a number of stems measured, the lowest part, which was 
beneath the water, varied from 4 to 10 mm. in diameter, while that 
above the water was from 10 to 20 mm. in diameter. The greatest 
difference found in a single plant was 6 mm. beneath and 18 mm. 
above the medium high water level. 
Los Banos, Philippine Islands 
I 
