72 Proceedings of Philosophical Societies. [July, 



glossy humour, which some physiologists suppose to proceed 

 from the old alburnum, and to contribute to the formation of 

 the liber, is not founded on convincing experiments. On the 

 contrary, when a portion of bark is removed from a tree, and 

 the wound is well robbed, so as neither to leave liber nor cam- 

 bium, neither the alburnum nor the wood produce any thing; 

 but the edges of the bark gradually extend themselves, cover 

 the naked wood, and produce liber and alburnum incontestably 

 proceeding from that bark. M. de Beauvois announces that he 

 will soon elucidate this proposition at full length, which hitherto 

 he has only noticed incidentally in his Dissertation on the Pith 

 of Vegetables. 



The opinion of physiologists has been hitherto very much 

 divided about the functions of the pith of vegetables. According 

 to some, that organ is necessary to the life of plants during the 

 whole of their existence : according to others, it is only useful 

 during the first years of their life, or all the time that it is green 

 and succulent, and may be easily confounded with the cellular 

 texture. M. de Beauvois has made on this subject observations 

 which tend to prove that the pith performs functions during the 

 whole life of the plant, if not absolutely necessary to its exist- 

 ence, at least very important for its progress, and the growth of 

 its branches, leaves, and especially of the organs necessary for 

 its reproduction. 



He has remarked that the circular layer, or fibres which 

 immediately surround the pith, has always a form correspond- 

 ing to the arrangement and disposition of the branches, twigs, 

 and leaves: that in plants with verticillated twigs and leaves, 

 for example, the horizontal section of this case of the pith shows 

 as many angles as there are twigs at each stage, and at each 

 verticilla. 



In like manner, the medullary case of the laurel rose pre- 

 sents an equilateral triangle, if the branch below the verticilla 

 has three twigs and three leaves ; but if we cut it under the 

 lower verticilla, where one of the twigs and leaves is usually 

 wanting, it has only two angles, and the vestige of a third. This 

 law is constant, even in herbaceous plants. 



M. de Beauvois has begun similar observations on plants, with 

 opposite, alternate, dichotomous, spiral, and pinnated leaves. 

 He expects to find in them the same relation between the 

 medullary case, and the disposition of the branches, twigs, and 

 leaves. For example, opposite leaves seem to require a round 

 medullary case, becoming oval, and having its extremities more 

 and more pointed the nearer it approaches to the insertion of the 

 branches and the leaves. When the leaves are alternate, the 

 circle is less perfect. The extremities become equally narrow, 

 but alternately, and each on the sidp where the branch is to 



