888 Scientific Intelligence. — Botany. 



would seem to require that the inflammable vapour should be, 

 as it were, prevented from expanding by the vital action, or else 

 that its emission continually renewed, should always keep it 

 dense, around the plant, in proportion as it tended to expand 

 in the external air, two states of things equally difficult to con- 

 ceive. So singular a fact, however, is known only in a general 

 way among botanists,; without their having observed it them- 

 selves, and accurate details of it are to be found only in Deter- 

 ville's Dictionary of Natural History, where Bosc thus says : 

 '' The extremities of the stalks, and the petals of the flowers of 

 the fraxinella, are filled with an immense number of vesicles fulf 

 of essential oil. On the hot days of summer they diffuse a strong 

 scented vapour, inflammable and so abundant, that if, towards 

 evening when a cooler air rendered it a little denser, we bring a 

 lighted taper near the fraxinella, there appears all on a sudden a 

 great light, which spreads over the entire plant, without injuring 

 it.'' Chance having afforded me an opportunity of witnessing 

 these phenomena of inflammation of the fraxinella, I determined 

 to study their cause and physical conditions. At first, supposing 

 with those who have described the matter, the reality of an 

 ethereal emanation which encompasses the plant, I instituted, 

 according to this view^ diff*erent experiments, but none with any 

 success. I then directed my attention to the examination of the 

 cortical vesicles, whence it was said that this inflammable atmo- 

 sphere emanated. These vesicles, when observed with the mi- 

 croscope, present the form of small bottles, terminated by a sort 

 of conical neck, tapering to a point at its extremity. They have 

 been very accurately described by M. Mirbel in his " Elements 

 of Vegetable Anatomy and Physiology."" These are found dis- 

 tributed more or less numerously over every part of the stalk : 

 they are seen in greater abundance on the peduncles of the 

 flowers, principally in their lower surface, at the extremity 

 where the flower is inserted ; we may still follow them on the 

 borders of the leaves of the calyx, on the borders and nerves of 

 the petals, and on the stamens and style ; in fine, their grains, 

 more condensed, thus cover all the surfaces of the ovaries, when 

 they are enlarged by fecundation. Among these utricles, some 

 are sessile, others pediculated, the latter in different parts, but 

 more frequently on the most vigorous. Very small at the com- 

 mencement of vegetation, they become enlarged according as 



