DEPARTMENT OF BOTANICAL RESEARCH. 73 



in size. Vacuoles had disappeared from the nucleoplasm and a thick- 

 ened granular layer was present in the peripheral portion. 



The most pronounced effects of desiccation and starvation were 

 exhibited by the cortex of Echinocactus. The changes noted as having 

 been seen in the palisade tissue were followed by the entire disappear- 

 ance of the protoplasts and the hydrolysis of the cell-walls. The con- 

 sequent disintegration of cell masses formed lacunse as large as 8 c.c. 



Some of the effects of desiccation and starvation were to be found 

 in the medulla of Echinocactus plants under treatment, but to a lesser 

 degree. Disintegration of cell-walls was observed in restricted areas. 

 No change appeared to be produced in the vascular bundles by desic- 

 cation and starvation. 



Early stages of the changes noted above, such as the reduction of 

 cytoplasm and nuclei of cells, deformation and peripheral thickening 

 of nuclei, and hydrolysis of cell-walls, were found in plants which had 

 been desiccated in diffuse light for only 10 months. 



An Echinocactus which had been desiccated for 42 months and then 

 placed vmder normal conditions in the soil for 22 months did not entirely 

 regain the normal condition. The epidermal system was fairly normal, 

 excepting irregularity in proportional thickness of anterior and pos- 

 terior walls of stomatal guard cells. Nuclei of the palisade cells were 

 below normal in size, and only one was seen that had regained normal 

 shape. The peripheral, thickened, granular layer was still present in 

 many cases. The cortex also retained irregularities of cell-wall and 

 nucleus, as effects of the starvation and desiccation. Recovery was 

 most advanced in the outer part of the cortical region. Cell-walls in 

 the outer cortex varied from 2 to 10 micra in thickness, while in the 

 inner cortex the variation was from less than 1 micron to over 20 micra. 

 The inner cortex of this recuperating plant was characterized by some 

 nuclei which were larger than the normal.^ 



The General Course of Depletion in Starving Succulents, by D. T. MacDougal. 



A series of tests to determine the rate, course, and extent of the water- 

 loss in massive succulents was begun in 1908. Selected individuals 

 of Echinocactus, Carnegiea, and other plants with a relatively large 

 water-balance, growing in the Tucson region, were taken from their 

 habitats and placed upon stands which supported the plants at the 

 height of a meter in such a manner that the light exposure was normal 

 as to angle. Some were put in this position in the open, exposed to 

 the full force of the sun, and were subject of course to the high midsum- 

 mer temperatures of the region. Others were placed in laboratory 

 rooms in which the illumination was from ordinary side-windows, and 

 the temperature was rarely altered by artificial heat, being in general 



*See MacDougal, Long, and Brown. End results of desiccation and respiration in succulent 



plants. Physiol. Researches, vol. 1, No. 6, 1915. 



