208 Miss Bale, On certain outgrowths {Intumescences) 



these efforts on the part of the plant might be sufficient, but 

 where the change to a damp atmosphere was permanent, patho- 

 logical conditions would supervene and ultimately death would 

 ensue. These pathological conditions would not be due to the 

 outgrowths, but to the inadequate transpiration (caused by damp- 

 ness) which checks metabolism. For example, the plant grown in 

 the Filmy Fern House became thus diseased without the formation 

 of outgrowths. 



It still remains to be proved whether, as seems most likely, 

 a moist atmosphere is the important factor, or a damp soil. 

 Hitherto authors do not seem to have distinguished between the 

 effects of damp air and damp soil. It seems probable that, if 

 the air be dry enough to allow of the necessary transpiration, a 

 damp soil might even promote the healthy growth of the plant. 

 If this be so then it follows that there is not actually too much 

 water in the plant, but that the plant cannot get rid of it. The 

 plant in the Cactus House seems to give evidence in favour of 

 this view. In this case the roots were kept dry, but outgrowths 

 appeared, probably because of the dampness of the atmosphere 

 in the Cactus House at the time. 



It is proposed to make further experiments next summer, in 

 order to determine the relation between the absorption of water 

 by the roots, and transpiration, and also to determine the relative 

 importance of light, heat and moisture as factors in promoting 

 or hindering the development of outgrowths. 



Note. The great variability in the hairiness of this species in 

 different parts of the world (see Floras of India, Africa, Australia, 

 Ceylon, &c.) may be connected with the question of transpiration. 



I would take this opportunity of expressing my grateful thanks 

 to Professor Marshall Ward for allowing me to work in the Botanical 

 Laboratory, and for the unfailing kindness and help which he has 

 continually extended to me during my investigations, which were 

 undertaken at his suggestion. 



My sincere thanks are also due to Mr Lynch, Curator of the 

 Botanic Garden, for the readiness with which he has helped me 

 to carry out my experiments, and for the care and trouble which 

 he has bestowed upon them. 



Explanation of Plates. 



(Plates VIII, IX, X.) 



Fig. 1. Young shoot, natural size, with outgrowths on the stems 

 and leaves. 



Fig. 2. Part of the stem (magnified about four times) shewing 

 outgrowths and also glandular and stiff hairs. 



Fig. 3. Young capsule (natural size) covered with outgrowths. 



