H. BOTANY AND HORTICULTURE. 291 



instance, where several specimens of Boletus were packed in 

 a box, it was found that the temperature of the air was raised 

 from seventy to seventy-five degrees, an increase readily ap- 

 parent to the hand. 12 A, September 8, 380. 



AKE FROZEN PLANTS KILLED IN FREEZING OR IN THAWING? 



The question whether a plant killed by frost is destroyed 

 while freezing or during the subsequent thawing is one that 

 has excited considerable interest on the part of physiologists,' 

 who have, however, in vain endeavored to answer it. Quite 

 unexpectedly, a method has been placed at the command of 

 experimenters that enables them to solve the problem satis- 

 factorily. In some tropical countries plants of the genus 

 jPhajus and Galanthe have long been known to contain indi- 

 go ; this, while they are living, being in the form of indigo- 

 white, or indigotin, the blue color exhibiting itself only after 

 death. If, for instance, the milky-white flowers of the Ga- 

 lanthe be crushed in the hand, they become instantaneously 

 blue, furnishing an excellent opportunity of showing the re- 

 lationship between indigo and indigotin. If, now, these flow- 

 ers be frozen, they immediately assume the blue color of in- 

 digo, appearing at first a pale blue, then darker, the pollen 

 masses alone retaining their natural yellow color throughout. 

 The cold air supplies the place of a reagent, and is, indeed, 

 more sensitive than any other that chemistry can produce. 

 The flower-stems, with their white bracts, are also changed 

 into blue. These experiments, more or less modified, have 

 been applied repeatedly to the plants mentioned, and to oth- 

 ers allied to them, and always with the definite result of 

 proving that death occurs during the freezing, and is not de- 

 ferred until the thawing out. Similar changes of color are 

 produced on these plants by such chemical agencies as cause 

 death in whole or in part, as by immersion in sulphide of car- 

 bon, ethereal oil, ether, etc. Concentrated solutions of hydro- 

 chlorate of morphia and nitrate of strychnine do not, howev- 

 er, cause this change, showing that they have comparatively 

 little noxious influence upon plants. 1 C\ xxvi., 1871, 412. 



CIRCULATION IN PLANTS. 



In conducting experiments upon the transpiration of fluid 

 by leaves, it is a matter of importance to determine the ra- 



