Lobed, in a special sense, when the incisions do not extend deeper than about half-way between the margin and the centre of the blade, if so far, and are more or less rounded; as in the leaves of the Post-Oak, Fig. [148], and the Hepatica, Fig. [152].
Cleft, when the incisions extend half way down or more, and especially when they are sharp; as in Fig. [149, 153]. And the phrases two-cleft, or, in the Latin form, bifid, three-cleft or trifid, four-cleft or quadrifid, five-cleft or quinquefid, etc., or many-cleft, in the Latin form, multifid,—express the number of the Segments, or portions.
Parted, when the incisions are still deeper, but yet do not quite reach to the midrib or the base of the blade; as in Fig. [150, 154]. And the terms two-parted, three-parted, etc., express the number of such divisions.
Divided, when the incisions extend quite to the midrib, as in the lower part of Fig. [151], or to the leaf-stalk, as in Fig. [155]; which really makes the leaf compound. Here, using the Latin form, the leaf is said to be bisected, trisected (Fig. [155]), etc., according to the number of the divisions.
Fig. 148, pinnately lobed; 149, pinnately cleft; 150, pinnately parted; 151, pinnately divided, leaves.
Fig. 152, palmately three-lobed; 153, palmately three-cleft; 154, palmately three-parted; 155, palmately three-divided or trisected, leaves.
[141.] The Mode of Lobing or Division corresponds to that of the veining, whether pinnately veined or palmately veined. In the former the notches or incisions, or sinuses, coming between the principal veins or ribs are directed toward the midrib: in the latter they are directed toward the apex of the petiole; as the figures show.
142. So degree and mode of division may be tersely expressed in brief phrases. Thus, in the four upper figures of pinnately veined leaves, the first is said to be pinnately lobed (in the special sense), the second pinnately cleft (or pinnatifid in Latin form), the third pinnately parted, the fourth pinnately divided, or pinnatisected.