4' 18 General Notices . 



not undergo the same singular change, but continue undiminished after the 

 seeds are niostl}' ripe, and probably, indeed, as long as the leaves themselves 

 retain their freshness. The acridity of the genus Helleborus is probably go- 

 verned by circumstances different from any of those already mentioned ; but 

 the experiments already made are insufficient to point out the true rule. In 

 the course of these observations many remarks were also made on the nature 

 of the acridity possessed by the different species, upon vi^hich incorrect ideas 

 at present very generally prevail ; several material corrections vrere also sug- 

 gested as to the general opinions respecting the influence of heat, desiccation, 

 and time upon their acridity; and a short allusion was made to the proper- 

 ties of a remarkably crystalline principle which the author discovered in one 

 of the species of Ranunculus, and which appeared to him to be the ingredient 

 upon which the activity of that genus depends. 



" The author next entered into some details regarding the influence of the 

 progress of vegetation on narcotic plants, and commenced with the natural 

 family Amygdaleee, the leaves of several of which are eminently poisonous, in 

 consequence of containing, or producing when bruised, a hydrocyanated essen- 

 tial oil. He showed that this oil abounds most in the leaves of the cherry 

 laurel (Cerasus Lauro-cerasus), when they are young and undeveloped ; and 

 that it goes on diminishing gradually in proportion to their weight, as they 

 increase in age and vigour, until the commencement of their second season, 

 when the old leaves, though plump and luxuriant, do not contain above an 

 eighth or tenth of what they contained in the infant state, or of what is con- 

 tained in the young undeveloped leaves of the same period. This is a com- 

 plete reversal of the generally admitted law in respect of the formation of 

 volatile oils in leaves, 



" The consideration of this fact led to some statements upon the mode and 

 form in which some essential oils and other active principles exist in the leaves 

 of plants ; and the conclusion was drawn, that in all probability many active 

 principles, which are separated from plants by simple processes, do not exist 

 ready-formed in the leaves ; but, as in the familiar case of the mustard seed 

 and bitter almond, are only developed when the structure of the leaves is 

 broken up, and principles of a different kind, secreted in distinct cells, are 

 brought in contact with one another or with water. 



'• The remaining departments of the investigation were postponed ; but 

 further observations were promised upon the influence of the progress of ve- 

 getation on the solanaceous and umbelliferous plants, and likewise on the effects 

 of soil and climate." 



From the above extract it may be gathered why cattle reject the J?anunculus 

 acris, or common buttercup of the meadow, while green, but do not object to 

 it, but are even said to be fond of it, in a state of hay. — Cond. 



Temperature of Plants. — M. Dutrochet, some 3'ears ago, proved by expe- 

 riment that living plants have a proper heat ; and other experiments have 

 recently been made by M. Van Beck, and read to the French Academy in 

 January last, confirming the fact. The maximum of inherent heat which M. 

 Van Beck found, on September 29th, an hour and a quarter after noon, in a 

 young leaf of Sedum Cotyledon, was about 23° centigrade, or about some- 

 thing more than half a degree of Fahrenheit. In rainy and dull days the heat 

 was not so great as when the weather was calm and clear. The following ob- 

 servations are interesting, as tending to show the probable advantages of a free 

 circulation of the air among plants ; though, as the writer observes, the sub- 

 ject requires to be farther examined. 



" A singular phenomenon, which I have always observed in the course of 

 my experiments, is, that, on suddenly raising the bell-glass which cut off all 

 communication betv/een the air of the apartment and that of the plant, the 

 heat of the latter always rose suddenly some tenths of a degree. This phe- 

 nomenon, however, lasted only a few minutes; the magnetic needle soon 

 retrograded, passing zero of the scale, and showing, by its opposite and per- 

 manent deviation, that the living plant had a much lower temperature than the 

 dead leaf, as is always the case in the atmosphere. 



