On the Buds and Ravij/icallons of Plan::. 323 



Is in an iininterrnpted relation with anslher zone of the 

 trunk, and seems to he thus produeed hv the proiontration 

 or increase of the latter. It appears to me that the cause 

 is explained bv the following- observation : — It is eenerallv 

 known that the cavihium, of which the liher is formed, has 

 its birth in the alhurmim and bark, and that the latter, 

 ■during the formation of the cambium, is altogether sepa- 

 rate from the alburnum even at the base of the branch. By 

 these nieans llie cambium of the trunk and that of the 

 branch are never divided ; on the contrary, they adhere to 

 each other, and the result is, that the wood thence arisinc?; 

 forms thus an nninterruptcd zone. The old trunlrs of the 

 pine, fir, oak, &c. seem, however, sometimes lo show the 

 contrary ; for it is not uncommon that the branches, even 

 those covered ^vith bark, traverse a greater or less part of tjie 

 wood of the trunk, without being there united to the exterior 

 zones. Nevertheless, if such a trunk be cut vertieallv, it 

 will be seen that all the zones of the branch have an im- 

 mediate reference to as many zones of the trunk 5 the reason 

 of which isj that this branch has been cut, or has ceased to 

 grow, and that the trunk, v.hich has continued its zones, 

 has surrounded and inclosed the branch sometimes even en- 

 tirely. 



It may perhaps be asked, why all the germs of a twis; do 

 not pierce the bark at the same time the first year. This 

 question I am not able to answer, because I cannot unveil 

 the mysteries of nature, and, in regard to the birth of buds, 

 know only the above phenomena. It may, iiowevcr, be 

 conjectured that in the expanded buds there were germs, 

 that is to say, prolongations of the medullary sheath, dif- 

 fering in size and vigour; and that, besides, the time of 

 their respective development depended on external circum- 

 stances, the most of \\hich arc still unknown to us. 



It is observed sometimes in shumac, the plane-tree, &c. 

 that the lateral prolongations are entirelv dried c\\-\A ligneous, 

 though that in the mi"ddle be still perfectly herbaceous. In 

 this case the petiole which covered the great prolon^iation, 

 and below which the bud that produces the twig must have 

 b<'en formed, has been torn or dropped oft" the preceding- 

 spring, or at least before the autumn. 



The means w hich nature has made choice of to nourish 

 the buds during the winter have been the object of several 

 hypotheses. 1 shall abstain from mentioning them all, in 

 order that I may attach myself to the only one wliieh nierits 

 particular consideration. The interior of the bud has been 

 compared to the embryo of a seed, and it has been a.sscrted 



that 



