640 
PHANEROGAMS, 
the leaf where the principal veins radiated On the adventitious buds on the leaves 
of Utricularia^ Pringsheim's treatise already quoted may be consulted. Adventitious 
buds more often spring from roots, e.g. in Anemone japonica, Linaria vulgaris, 
Cirsium arvense, and Populus tremula, according to Irmisch I The shoots which 
spring from the bark of the older stems of trees must not at once be set down as 
the development of adventitious buds ; since the numerous dormant buds of woody 
plants may long remain buried and yet retain their vitality. 
The Leaves of Dicotyledons exhibit a greater variety both in their position and 
their form than those of all other classes of plants put together. The ordinary 
phyllotaxis of seedlings begins with a whorl of two cotyledons, and continues 
either in decussate pairs or passes into a distichous arrangement or into whorls 
consisting of larger numbers or spiral arrangements with the most various angles 
of divergence. More simple arrangements, especially that of decussate pairs, are 
generally constant in whole families, the more complicated arrangements usually less 
constant. Axillary branches usually begin with a pair of leaves which are either 
opposite or alternate, and stand right and left of the median line of the mother-leaf. 
It is quite impossible to give in a short space even a general account of the 
forms of leaves, even apart from cataphyllary leaves (scales on underground 
stems and those which envelope persistent buds), hypsophyllary leaves or bracts, 
and floral leaves ; only a few of those forms of foliage-leaves can be mentioned 
here which are peculiar to or characteristic of Dicotyledons. The foliage leaves 
are usually divided into a slender leaf-stalk {petiole) and a flat blade {lamina) ; the 
lamina is very commonly branched, i. e. lobed, pinnate, compound, or incised ; and 
even where it forms a single plate (simple leaf) the tendency to branching is gene- 
rally indicated by indentations, teeth, or incisions in the margin. The branching' 
of the lamina has usually a distinctly monopodial origin, but its development may 
continue in a cymose manner, a helicoid succession of lateral lobes being formed 
on each side right and left of the centre of the leaf (as in Rubus, Helleborus, 
&c., see Fig. 141). The sheathing amplexicaul base is not common in Dicotyledons 
(but occurs in Umbelliferae) ; and the occurrence of Stipules in its place is more 
common. The cohesion of opposite leaves into a single plate pierced by the stem 
is not uncommon (' perfoliate ' leaves, as in Lamium amplexicaule, Dipsacus Fullonum, 
Lonicera Caprifolium, species of Silphium, Eucalyptus, &c.) ; as well as the downward 
prolongation of the lamina of the leaves (' decurrent leaves '), which distinguishes the 
* winged ' stem of Verbascum, Onopordon, Sec. The not uncommon ' peltate ' leaf also 
scarcely occurs in so marked a manner in any other class [TropcBolum, Victoria regia, 
&c.). The power of Dicotyledons to develope from their foliage-leaves organs of 
the most diverse functions adapted to the most various conditions of life is seen in 
a very striking manner in the common occurrence of leaf-tendrils and leaf-spines, 
and still more in the formation of the ascidia or ' pitchers ' of Nepenthes, Cephalotus^ 
Sarracenia, &c. 
Saxifraga granulata, Dentaria bulbifera, Raituncjihis Ficaria, Sec. [Berge, Ueb. Bryoptiyllum calycinum, 
Zürich 1877.] * 
* The common method of propagating Begonias is by cutting or tearing the leaf, which, if then 
placed on moist soil, produces buds on the edges.] 
^ [Irmisch, Bot. Gaz. III. pp. 146 and 160.] 
