TRANSACTIONS OF SECTION K. 931 
developed intumescences, and were all very much alike. When each had about 
nine or ten leaves, and was beginning to flower, the plants were placed under 
different conditions, and examined at the end of six weeks :— 
The plant grown in the open was entirely free from intumescences ; it was par- 
ticularly vigorous, and had strong lateral branches. 
The plant in the temperate house had outgrowths only on the wnder sides of 
the leaves, and on the flowers and fruits. 
The plant in the filmy fern-house was very unhealthy, but had no outgrowths. 
All the other plants had outgrowths on one or both sides of most of the leaves, 
on the stems, the green parts of the flowers, and on the young fruits. 
Conelusions, 
As far as the evidence goes at present, it seems to point to the conclusion that 
the intumescences are pathological, and are due neither to insects nor to fungi, 
but to the direct effects of environment. The formation of outgrowths appear to 
be caused by excessive moisture combined with a high temperature. If the 
temperature is low the plants do not appear to have strength to form them. The 
production of outgrowths seems to be a response on the part of the plant to 
insufficient transpiration. 
Note—Similar, but less well-marked, outgrowths were observed on the leaves 
of plants of Ceratotheca triloba. As in the case of Hibiscus vitifolius, they were 
not formed in a plant placed in the open ground. 
Outgrowths which may prove to be of the nature of those in Hibiscus vitifolius 
have been described by Sorauer in Dracena (angustifolia, &e.), Cassia tomentosa, 
Acacia (semperflorens, &c.). 
a 
