B. ESTHER STRUCKMEYER I7I 



(4) reported its effect on cell structure in bean plants. With the appUca- 

 tion of this growth substance there was increased cambial activity in 

 the stem resulting in the formation of thick-walled xylem cells. A greater 

 number of Hgnified cells were present as compared with the control. 



It was observed that stems of cocklebur grown without a calcium 

 supply generally had smaller and thinner-walled cells. This was especially 

 conspicuous in the xylem cells, xylem parenchyma cells, and pericycle 

 fibers where there was decreased hgniiication. In fact vessels frequently 

 collapsed because of lack of rigidity of the cell wall. Alpha-naphthalene- 

 acetamide induced a thickening and hgnification of cell walls when 

 sprayed on or apphed in lanolin to the plants grown without calcium. 

 The first experiment was conducted at a temperature of 70° F. The plants 

 were eight inches tall when the treatment was started. A series of cockle- 

 bur plants was set up, some of which were given a complete nutrient 

 solution, a nutrient lacking calcium, a complete nutrient and a spray 

 treatment with a-naphthaleneacetamide, and a nutrient lacking calcium 

 but also receiving an a-naphthaleneacetamide treatment. Thirty-six days 

 from the start of the experiment severe symptoms were apparent in 

 plants grown without calcium. At the same time plants grown without 

 calcium but sprayed with a-naphthaleneacetamide showed no symptoms 

 like curling of the leaves near the stem apex or a spotted appearance of 

 the leaves. Plants given the other two treatments appeared normal. 



The anatomical structure of the fourth internode of plants given a 

 complete nutrient supply showed the usual organization of the cells 

 (Fig. 20). An active cambium differentiating phloem and xylem was 

 apparent. Plants lacking calcium in the nutrient solution showed all 

 cells to be smaller and thinner walled; the xylem elements were fewer 

 and less hgnified; the vascular bundles were small with few vessels; 

 and the cambium was less conspicuous (Fig. 21). 



Plants given a complete nutrient solution and treated with a-naph- 

 thaleneacetamide showed an active cambium differentiating vascular 

 elements (Fig. 23). Xylem elements, especially tracheids, were thicker 

 walled than in the control, and increased thickening of the phloem fibers 

 was also evident. Plants grown without calcium and treated with a- 

 naphthaleneacetamide showed no deficiency symptoms thirty-six days 

 after treatment. The fourth internode of these plants showed anatomical 

 characteristics resembling those of normal untreated plants. The vas- 

 cular bundles were shghtly smaller than in the control plants, but the 



