1869.] Botamj, &c. 423 



M. Prillieux produced the same results in a model). A certain 

 state of the tissues is indispensable to their manifestation; they 

 can only be produced at that period of development when the 

 tissues are sufficiently flexible; but it is, nevertheless, undeniably 

 true that they are due to a physical cause. 



The Sleep of Plants. — In an exhaustive essay on this curious 

 subject, of much physiological importance, M. Koyer reviews the 

 opinions of those who have written on the question, and adduces a 

 great number of facts in illustration of the various causes which 

 produce the sleep of leaves and of flowers. These, he maintains, are 

 not quite identical. He distinguishes a dim*nal sleep as weU as a 

 noctm'nal for plants equally with a^iimals. . Heat, light, and tur- 

 gescence, are influential in aftecting the sleep of leaves — only heat 

 and turgescence in the sleep of the corolla — by their excess or 

 diminution. Flowers when they sleep assume the form of their 

 characteristic aestivation, just as many animals assume the position 

 they occupied in utero. The inclination of flowers to the sun 

 depends on the peduncle, not on the flower at all. 



Excretion of Cay-bonie Acid hy Plants. — Mr. Broughton, 

 Chemist to the Cinchona Plantations of the Madras Government, 

 has made, with a Sprengel's an-pump, some important observations 

 as to the exhalation of CO^ by plants — a phenomenon which was 

 well known to occur in the night. The experiments were made 

 mostly on cut portions of the plants, but experiments were also 

 made for control on plants as they actually grow. Sometimes the 

 deprivation of oxygen was efl'ected by substituting lor air an atmo- 

 sphere of hydrogen or nitrogen ; whilst comparative experiments 

 were made on plants supphed with air that had been freed from 

 carbonic acid. The main conclusions to which he was led are 

 enimciated by the author as follows : * — 



1st. That nearly all parts of growing plants evolve carbonic 

 acid in considerable quantities, quite independent of direct oxi- 

 dation. 



2nd. That this evolution is connected with the life of the plant. 



3rd. That it is due to two causes, namely, to previous oxidation, 

 resulting, after a lapse of time, in the production of carbonic acid, 

 and to the sepai-ation of carbonic acid from the proximate principles 

 of the plant while undergoing the chemical changes incident to 

 plant-growth. 



The Bestir ation of Aquatic Plants in Darhiess.—M.. Deherain 

 has pointed out that when aquatic plants are kept in darkness they 

 are hterally asphyxiated ; for on making examination of the water 

 in which they have died, he has found absolutely no trace of oxygen, 

 but only carbonic acid and nitrogen. In a pond where a very dense 



* 'Proceedings Eoyal Society,' April 29th. 



