AGRICULTURAL BOTANY. 327 



colored illuminations on the position and texture of the leaves, development 

 of the mesophyll. palisade parenchyma, chloroi)Iasts, stems, etc., are discussed 

 at some length. 



The author concludes that the favorable effect of yellow and green light on 

 plants is due not only to their thermal effect, but also to the fact that these 

 two colors of light more nearly approach white light in their illumination. 



The closing response in Dionaea, W. H. Brown and L. W. Sharp (Bot, Gas., 

 Ji9 (1910), No. Jf, pp. 290-302, dgm. J). — A study has been made of D. muscipula 

 to determine the cause of its closing response. This was found to depend on 

 the intensity rather than on the number of stimuli. 



"Response is normally brought about by the compression of certain cells at 

 the bases of the sensitive hairs, but the compression of other cells of the blade 

 also causes closure, and it is probable that the latter cells are equally sensitive 

 with the cells at the bases of the hairs, as is indicated by electrical and thermal 

 stimulation. 



" The closing response follows the application of mechanical, electrical, and 

 thermal stimulation. It also follows a combination of stimuli of two kinds when 

 consecutively applied, the individual stimuli being of an intensity such that 

 either alone would be insufhcieut. 



" The effect of mechanical stimulation is due to compression of cells, and not 

 to contact with a hard object, continued pressure, or release of pressure. The 

 failure of the leaf to respond to shaking is probably connected with the small 

 inertia of the sensitive hairs, and the slight resistance offered i>y the air to their 

 passage through it. 



" Water at room temperature causes closure only when it bends a sensitive 

 hair. 



"After one mechanical stimulus there is a short period during which a second 

 mechanical stimulus is ineffective." 



The efEect of aqueous solutions of electrolytes on germination, H. Micheels 

 (Acad. Roll. BtUj.. Bid. (7. Sci., 1909, Xo. 11, pp. KHli-l 1 IS) .~-\ report is given 

 of studies on the influence of solutions of certain electrolytes on the germina- 

 tion and early growth of wheat. The experiments were carried on with solu- 

 tions of potassium chlorid, potassium nitrate, potassium hydroxid, sodium 

 ehlorid, sodium nitrate, calcium carbonate, magnesium chlorid, aluminum 

 chlorid, and other salts, representing different osmotic pressures, the salts 

 being used singly and in various combinations. 



In studies with monovalent, divalent, and trivalent cations, as represented by 

 N/100 and N/1000 solutions of sodium chlorid, magnesium chlorid, and alumi- 

 num chlorid, the mf)st favorable results were obtained with the most dilute 

 solutions. Comparisons between N/10, N/'lOO, and N/1000 solutions of sodium 

 chlorid showed that the N/100 solution was the most favorable to germination 

 and growth of the seedlings. In a similar manner it was found that N/100 

 solution of potassium chlorid, and N/1000 solutions of potassium nitrate, 

 potassium hydroxid, and calcium nitrate gave the best results. Where mix- 

 tures of N/100 solutions of potassium chlorid and potassium nitrate were tested 

 the combination was less favorable to growth, as expressed by the length of the 

 roots, than either of the salts used alone. The combination favored the develop- 

 ment of root hairs as compared with potassium nitrate, although the roots were 

 shorter. The leaves, where the two were combined, were intermediate between 

 those produced in the simple cultures. 



When sodium nitrate and potassium nitrate in N/100 solution were compared 

 with mixtures of the two, the mixture of the two salts was found decidedly 

 favorable, the sodium compound having exercised a protective effect. Addi- 



