430 EXPERIMENT STATION RECOED. 



End results of desiccation and respiration in succulent plants, D. T. Mac- 

 DouGAL, E. R. LoxG, and J. G. Bbown (Phyaiol. Researches, 1 (1915), No. 6, pp. 

 289^25, pis. 3, figs. 5; abs. in Science, n. ser., 42 (1915), No. 1094, PP- 879. 

 880). — The authors give an account of experiments in which a hirge number of 

 sound individuals of Echinocactus and several joints of Opuntia were deprived 

 of water supply and compelled to carry on existence at the expense of accumu- 

 lated water and food material. 



It was found that an Echinocactus in the open may survive for no more 

 than two years on its own supply of food material and water, while similar 

 plants in diffused light have remained sound after six years of starvation. 

 Nonreducing soluble sugars are said to be present in only minute proportions, 

 if at all, in normal Echinocacti, but are noticeable constituents of the sap of 

 desiccated ones. Extended desiccation and starvation made no alteration in 

 the integument of Echinocactus, but in a plant which had been thus treated 

 for 73 months the cuticle was thicker than normal, while the outer wall of 

 the epidermal cells was thinner. The cytoplasm and nuclei in the epidermal 

 system were reduced, but new cork layers were being formed as in normal 

 plants. The stomata remained permanently open and many were in a col- 

 lapsed condition. The palisade layer was thinner than in normal plants, the 

 cytoplasm reduced to small masses in the angles of the cells, and the nuclei 

 deformed and reduced in size. The most pronounced effect of starvation was 

 exhibited by the cortex of Echinocactus. 



Distribution of cacti with, reference to the role played by root response, 

 W. A. Cannon (Abs. in Sciaice, n. ser., 42 (1915), No. 1094, P- 811). — Accord- 

 ing to the author's observations in southern Arizona, roots of cacti lie close to 

 the surface of the soil and are subject to the maximum temperature changes, 

 including the highest temijeratures of the summer season. Experiments show 

 that a high temperature is necessary for the best growth of the roots of cacti, 

 and as active root growth takes place in midsummer it is suggested that the 

 cacti as a family are limited to such regions as have summer rains, other con- 

 ditions being favorable. In other regions of abundant moisture, but without 

 the rains which characterize the warm season, cacti are either wholly wanting 

 or constitute an insignificant part of the vegetation. 



The distribution and succession of the flowers of the giant cactus in rela- 

 tion to isolation, D. S. Johnson (Abs. in Science, n. ser., 42 (1915), No. 1094, 

 p. 876). — The author states that the flowers of the giant cactus growing about 

 Tucson, Ariz., are rarely syranjetrically gi-ouped about the growing point of the 

 stem. They are said to be generally most abundant on the east side and usually 

 wanting on the west side. This phenomenon is considered to be brought about 

 by differences in sunlight and air temperatures, the east side of the trunks 

 being warmer than the west side. 



The personation and multiplication of the fruits of certain Opuntias, D. S. 

 Johnson (Abs. in Science, n. ser., 42 (1915), No. 1094. pp. 878. S7.'M.— Attention 

 is called to the fact that the fruits of certain cacti differ from those of most 

 seed plants in not falling from the tree at the end of the growing season. In 

 some forms, of which O. fulgida is one of the most striking examples, the fruit 

 remains attached and growing, season after season. Primary flowers are formed 

 from the lateral buds of the last year's branches. These shed the perianth live 

 or six days after opening, and give rise to fruits which not only remain attached 

 but also give rise to buds of secondary flowers. If these persistent fruits are 

 allowed to remain attached they give rise only to flower buds, but if they are 

 broken off and placed on moist soil the same areolie develop roots, send out 

 branches, and so start a new plant. 



