

INTUMESCENCES 



127 



size, lifting up the epidermis. In the stage shown in fig. 

 2, the epidermal cells had shriveled and were practically 



increasing 



indistinguishable. Successive stages show an 

 development of giant cells, and a condition after six or 

 seven days as shown in plate 28. Protruding from the 

 surface of the leaf were large masses of enormously elon- 

 gated very thin-walled cells in a condition of vigorous devel- 



opment. Th 



been entirely broken away, 



and growth was taking place directly out from the center 

 of the mass of tissue and in a lateral direction. The outer- 

 most cells, in the stage shown on plate 28, were gradually 

 drying. The giant cells themselves were very thin-walled, 

 closely packed together and practically empty, that is, they 

 were filled with air. In the lower ones, that is those well 

 within the leaf body, very much reduced chlorophyll grains 

 could be found. The whole structure had the appearance 

 of the bodies originally described by Sorauer 26 , and called 



by 



intumescences. There were no 



signs of either 

 fungi or bacteria in the early stages of the wart forma- 

 tion. A study of the drawing shown on plate 28 explains 

 the peculiar outward appearance of the warts, the central 

 body being the cells growing perpendicularly to the surface 

 of the leaves, and the apparent rays constituted by the 

 lon<r hairlike cells pushing out from either side of the cen- 

 tral cells. The whitish appearance is explained by the 

 fact that the cells were full of air. 



The giant cells originated at first in the outer spongy 

 parenchyma layer, but as the growth progressed, the 

 palisade cells likewise 



started to enlarge so 



that in 



the 



later stages the entire mesophyll contributed to the for- 

 mation of the oedematous cells. 



Since the formation of the first warts, just described, 



agree in 



others have been produced artificially. They 

 most respects with those first formed, with one possible 

 exception. It was found that the size and shape of the 

 warts could be modified at will, depending upon the man- 



i ' 





