ARRANGEMENT. 



83 



a. The vernation of the leaf is exliibited in a most interesting manner, by 

 making, mth a keen instrument, a cross-section of the bud in its swollen state) 

 just before its expansion ; or it may be well observed by removing the scales. 



217. The forms of vernation are mostly similar to those of aestivation (108), 

 and arc expressed by similar terms. Some of the principal are the following : 



FIG. 27. — Forms of venialion. The numbers agree 

 with llie corresponding paragraphs. 



1. Equitant, overlapping each 

 other in a parallel manner, vdth- 

 out any involution, as in the 

 leaves of the Iris. 



2. Obvobite, one of the margins 

 of each leaf interior and the 

 other exterior to the margin of 

 the leaf opposite. Ex. sage. 



3. Involute, having the edges 

 rolled inwards. Ex. apple, \'iolet. 



4. Rcvolute, the margins rolled outwards or backwards. Ex. ^villow, rosemary. 



5. Convolule, the leaf wholly rolled up from one of its sides, as in the cherry. 



6. Plaited, each leaf folded like a fan. Ex. vine, birch. 



7. Circiiiaic, when rolled downwards from the apex. Ex. sundew, fern. 



§ 2. ARRANGEMENT. 



218. In regard to their insertion upon the axis, the an-ange- 

 ment of the young leaves in the bud is nearly or quite circular, 

 but by the development of the axis, tliis arrangement is modi- 

 fied in various ways, and the leaves are then said to be 



1. Scattered, or irregular, as in the potatoe. 



2. Alternate, one above the other, on opposite sides. Ex. pea. 



3. Opposite, two against each other at the same node (172). 



Ex. Hydrangia. 



4. Verticillate, or whorled, more than two in a circle at each 



node. Ex. meadow lily. 



5. Fasciculate, or tufted, in crowded whorls, or spires. Ex. 



Callitriche. 



219 We have formerly shown how some of these modes of arrangement may 

 be reconciled with the spiral (174, a), and we here add, diat, in general, when the 

 leaves are said to be scattered or alternate, they will be found, by the attentive 

 observer, to be strictly, though perhaps u-regularly, spiral ; — always so in the 

 annual shoot. 



a. Thus in the potato-vine, above cited, or in the house-leek, poplar, &c., if we 

 commence at the lower leaf, and draw a line to the next above it, thence to the 

 next and so on to the sixth leaf, we shall have gone just once around the stem, 



