Apr. 22, 1918 Intumescences 255 



succinctly be presented by quoting the author's terse summary, in 

 which he says (p. 190-191): 



A state of oedema is induced whenever, in the presence of an adequate supply of 

 water, the capacity of the colloids of the tissues for holding water is increased above 

 that which we are pleased to call normal. Any agency capable under conditions 

 existing in the body, of thus increasing the hydration capacity of the tissue colloids 

 constitutes a cause of oedema. The accumulation of acids within the tissues brought 

 about either through their abnormal production, or through the inadequate removal 

 of such as some consider normally produced in the tissues, is chiefly responsible for 

 this increase in the hydration capacity of the colloids, though the possibility of ex- 

 plaining at least some of it through the production or accumulation of substance (of 

 the type of urea, pyridin, certain amins, etc.) which can hydrate colloids as can 

 acids, or through the conversion of colloids having but little capacity for water into 

 such as have a greater capacity must also be borne in mind. 



DESCRIPTION OF INTUMESCENCES FOLLOWING INJURY 



During the early part of June, 191 7, a windstoi-m of sufficient velocity 

 to break dov\^n trees of considerable size occurred in the vicinity of 

 Raleigh, N. C. A few days later, the writer, on a field trip into the sandy 

 lands east of the city, noted that the leaf surface of cabbage (Brassica 

 oleracea capitata), particularly the lowermost leaves and the tips of the 

 inner leaves, were covered with numerous irregularly disposed, wartlike 

 prominences (PI. 18, A). The individual outgrowths were hemispherical 

 to short cylindrical in shape, yellowish to grayish in color, and projected 

 from the surface of the leaf in a sharply defined circle. They ranged in 

 size from mere points to structures having a diameter of 3 mm. and in 

 extreme cases projected from the leaf surface as much as twice the 

 thickness of the cabbage leaf. A depression corresponding to the promi- 

 nence commonly appeared on the opposite leaf surface. In some places 

 the outgrowths were so numerous as to merge into each other and conse- 

 quently appeared like one large, irregular intumescence. 



Microscopic examination of these intumescences shows that they begin 

 as small swellings of the epidermis. Soon the palisade parenchyma 

 beneath, or the spongy parenchyma, depending upon whether the intu- 

 mescence originates on the upper or lower leaf surface, is involved, and 

 the cells begin to become enlarged. At this stage the epidermis is broken 

 or elevated on the surface of the growing projection. Some of the 

 epidermal cells then shrivel and dry and remain as fragments on the 

 surface of the intumescence, while others are included in the intact 

 swollen tissues. Meanwhile the cells beneath have continued to enlarge 

 and all of the subjacent mesophyll comes to be involved in the formation 

 of the edematous cells. These cells are enlarged to many times their 

 normal volume (fig. i), are elongated, very thin-walled, and are practi- 

 cally destitute of chloroplasts and other protoplasmic contents. There 

 appears to be no tendency toward suberization, as is indicated b)' negative 

 tests with alkannin. The cells are not to be regarded as giant cells in 



