THE LEAF-BUD. 



85 



Walking-fern emits rootlets and buds at its apex ; the leaf of 

 Bryophyllum from its margin each bud here also preceded by a 

 rootlet. Some plants are thus artificially propagated in conser- 

 vatories from the influence of heat and moisture on a leaf or the 

 fragment of a leaf. 



252. Vernation or praefoliation are terms denoting the 

 mode of arrangement and folding of the leaf organs composing 

 the bud. This arrangement is definitely varied in different or- 

 ders of plants, furnishing useful distinctions in systematic botany. 

 It may be studied to excellent advantage by making with a keen 

 instrument a cross-section of the bud in its swollen state, just 

 before expansion ; or it may be well observed by removing one 

 by one the scales. The Forms of Vernation are entirely analo- 

 gous to those of ./Estivation, and denoted by similar terms. 



253. Vernation is considered in two different aspects first, the 

 manner in which the leaf itself is folded ; second, the arrange- 



* - * O 



ment of the leaves in respect to each other. This depends much 

 upon the phyllotaxy. ( 261.) 



Vernation, 277, of Oak leaf; 273. of Liriodendron (Tn Tip tree), 



282, Iris. 



279, of Fern ; 280, of Carex ; 281, 



254. Each leaf alone considered is either flat and open, as in 

 the mistletoe, or it is folded or rolled, as follows : viz. ^Reclined, 

 when folded crosswise, with apex bent over forward toward the 

 base, as in the Tulip-tree ; Conduplicate, when folded perpen- 

 dicularly, with the lateral halves brought together face to face, 

 as in the Oak ; Plaited, or Plicate, each leaf folded like a fan, 

 as in Birch. 



255. Circinate implies that each leaf is rolled or coiled down- 

 ward from the apex, as in Sundew and the Ferns. 



256. The Convolute leaf is wholly rolled up from one of its 



