38» Imperial Imtitute of France^ 



capable of reproducing, by means of" the cambium, the libei^ 

 and the bark necessary for covering it, as the bark produces 

 habitually, and even when it is partly removed from its 

 trunk, liber and soft wood. In this point he has for his 

 antagonist our colleague M. Palisot de Beauvois, who has 

 also directed his attention to these difficult questions re- 

 specting the progress of the sap and the formation of the 

 wood. According to this botanist, this oozing out of a 

 glairy matter, which some physiologists suppose to flow 

 iroui the old wood, and which contributes to ihe formation 

 of the liber, is not founded upon real experiments. On tliei 

 contrary, when part of the bark of a tree has been removed, 

 and the wound well rubbed, so as to leave no liber nor 

 cambium, neither the soft wood nor the wood itself pro- 

 duces any thing, but the lips of the solution of continuity 

 made in the bark stretch out, cover the wood left bare, and 

 then produce liber and soft wood incontestably emanating 

 from this bark. M. de Beauvois announces that he will 

 soon explain this proposition fully, which he has merely 

 hinted at in a memoir on the marrow of vegetables. 



The opinion of physiologists has been hitherto much 

 divided, as to the utility and functions of the pith of 

 vegetables. According to some, this organ is necessary to 

 the life of the plants during their whole existence : ac- 

 cording to others, it is useful to them only during the 

 first year and only during the whole of the time that it is 

 green and succulent, and when it may be still easily con- 

 founded with the cellular texture. 



M. de Beauvois has made upon this subject some obser- 

 vations which tend to show that the marrow exercises, 

 during the whole life of the plants, functions, if not of 

 an absolute necessity to their existence, at least very im- 

 portant to their progress, and the development of their 

 branches, leaves, and particularly the organs necessary for 

 their reproduction. 



He has remarked that the medullary canal, i.e. the cir- 

 cular layer of fibres which immediately surround the mass 

 of the pith, has always a form corresponding to the ar- 

 rangement and the disposition of the branches, boughs, 

 and leaves } that in the vegetables with vertical furrowed 

 {verlicillces) boughs and leaves, for instance, the horizontal 

 section of the medullary tube shows as many angles as 

 thete are boughs at each stage and at each verticille. 



Thus the medullary canal of the red laurel presents an 

 equilateral triangle if the branch below the verticilles ha"; 

 three boughs and three leaves; but if we cut it below the 



lowest 



