on the green parts of Hibiscus vitifolius Linn. 199 



Pit, at the Cambridge Botanic Garden. From these seeds eight 

 seedlings were obtained, and were, in January 1899, planted out, 

 each in a separate pot, and allowed to grow on, at first in the 

 Tropical, and later in the Intermediate Pit, until June 1899. 



Even when the seedlings were so young that they only 

 possessed two foliage leaves in addition to the cotyledons, these 

 leaves began to develope small outgrowths (fig. 21) which appeared 

 merely as a roughness on the upper surface. 



On June 8th the following observations were made. The 

 seedlings, which had been growing under identical conditions, 

 very closely resembled one another. Each had from eight to ten 

 leaves on the single main stem, and was beginning to put out, 

 in the axils of the lower leaves, small branches, and in those of the 

 upper leaves, solitary flowers. 



The first five or seven leaves were entirely free from out- 

 growths, one or two just above these had a few, two or three still 

 higher up were thickly, in some cases very thickly covered, while 

 the youngest leaves at the top were as yet unaffected. 



On June 9th the eight young plants were placed under varying 

 conditions, viz. : — 



One in the Garden in an open situation. 

 Temperate House. 

 Water-Lily House. 

 Tropical Orchid House. 

 Cactus House. 

 Filmy Fern House. 

 Two were left in the Intermediate Pit. 



On July 24 the plants were all again examined with a view 

 to determining the effects produced upon them by the altered 

 conditions. 



The Plant in the open ground. The most striking results were 

 obtained from this plant. It had completely lost all trace of out- 

 growths and become exceedingly vigorous and healthy. Its leaves, 

 instead of drooping, were spread out fiat and almost horizontally 

 and were much darker in colour than those in the houses. 



The Plant in the Temperate House. This differed from all the 

 others in having outgrowths exclusively on the under sides of the 

 leaves. It had however a few outgrowths upon the stem and 

 some large ones on the green capsules. 



The Plant in the Water- Lily House. This had a few outgrowths 

 on the under sides of the first four remaining leaves 1 , a larger 



1 It should be noted that by this time some of the older leaves at the base of 

 the stem had fallen off. 



