. Introduction to structural and systematic botany, and vegetable physiology. Botany. THEIR FORMS. 159. dantly developed, as in fact happens in the upper leaves of the same species when they grow out of water, and is shown in the same figure, they are merely cleft or lohed. If these lohes grow together nearly to the ex- tremity of the principal veins, the leaf is only toothed, serrated, or crenated; and if the small re- maining notches were filled with parenchyma, the leaf would be en- tire. The study of the development of leaves, however, proves that the parenchyma grows and shapes the outlin
. Introduction to structural and systematic botany, and vegetable physiology. Botany. THEIR FORMS. 159. dantly developed, as in fact happens in the upper leaves of the same species when they grow out of water, and is shown in the same figure, they are merely cleft or lohed. If these lohes grow together nearly to the ex- tremity of the principal veins, the leaf is only toothed, serrated, or crenated; and if the small re- maining notches were filled with parenchyma, the leaf would be en- tire. The study of the development of leaves, however, proves that the parenchyma grows and shapes the outlines of the organ in its own way, irrespec- tive of the framework, which is, in fact, adapted to the parenchyma rather than the parenchyma to it. The principal terms which designate the mode and degree of division in simple leaves may now be briefly explained, without further reference to this or any other theory. 282. A leaf is said to be serrate, when the margin is beset with sharp teeth which point forwards towards the apex (Fig. 254) ; dentate, or toothed, when the sharp salient teeth are not directed towards the apex of the leaf (Fig. 255); and crenate, when the teeth are rounded (Fig. 248, 256). A slightly waved or sinuous margin is said to be repand (Fig. 257) ; a more strongly uneven margin, with alternate rounded concavities and convexities, is termed sinuate (Fig. 258). When the leaf is irregularly and sharply cut deep into the blade, it is said to be incised (Fig. 259); when the portions (or segments^ are more definite, it is said to be lohed (Fig. 260, 264); &TidithBte,r[DS,two-lohed,three-lobed{'Fig,2Qi),five-lobed, &c., express the number of the segments. If the incisions extend about to the middle of the blade, or somewhat deeper, and especially if the sinuses are acute, the leaf is said to be cleft (Fig. 261, 265) ; and the tenns two-cleft, three-cleft (Fig. 265), &c. (or in the Latin form, bifid, trifid, &c.), designate the number of the segments:
Size: 1907px × 1311px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorgra, bookcentury1800, bookdecade1850, booksubjectbotany
