42 BUDS. 



medullary sheath. His hypothesis is founded on no better basis 

 than that of Duhamel. Mr. Nuttall believes that buds are pre- 

 organized germs, but that they have their origin in the first 

 development of the stem or branch on which they put forth. 

 There are decided objections to this theory, but our space for- 

 bids our entering into a discussion on the subject, or even 

 fully stating the theories alluded to. 



75. The structure of the adventitious buds is, in all respects, 

 like the normal or axillary buds, having pith in their center, 

 surrounded by spiral vessels, and inclosed by woody fiber and 

 cellular integument. From the existence of spiral vessels in ad- 

 ventitious buds which arise from the root, we derive a strong ar- 

 gument in favor of the existence of spiral vessels in the latter or- 

 gan, under a very slightly modified form ; and from this and 

 various other circumstances, we are led to believe that the con 

 stitution of the root and the stem is essentially the same, the 

 difference observed being occasioned by the media in which they 

 are developed. We have seen the common red plum, in the 

 loose earth of a garden, put forth buds from a root with as 

 much regularity as from the branches. 



76. The buds seem to possess, in some respects, the nature of 

 seeds, although in others they differ. The seed produces the 

 species or original type, while the bud perpetuates the variety; 

 hence the practice of grafting choice fruit. The bud will con- 

 tinue the characters of the individual variety, while the seed 

 would produce merely the species, with perhaps none of the 

 peculiarities of the plant from the fruit of which the seed was 

 taken. 



77. The manner in which the rudimentary leaves are folded 

 up within the buds, is a subject of much curiosity and interest. 

 Although the arrangement in different plants is very unlike, yet 

 in the same species there is a remarkable uniformity. , This 

 subject has been termed vernation, or gemmation, or prarfoliation. 



(1.) Appressed • in which the surfaces of the leaves are applied 

 to each other without being rolled, as in the Misletoe. 



(2.) Conduplicate ; when the leaves are folded inwardly upon 

 themselves, and placed side by side, as in the Rose. 



(3.) Imbricate ; where they lie over each other, breaking joints, 

 if we may use the expression ; that is, when the middle of one 

 leaf corresponds to the margin of the two within it, as in the 

 Lilac. 



75. What is the structure of adventitious buds? — 76. What do buds re- 

 semble? How do they differ? — 77. What is vernation ? When appressed? 

 Conduplicate ? Imbricate ? 



