. The essentials of botany. Botany. 298 BOTANT. 3. Elliptical, wliicb is longer than broad, lias base and apex equal, and sides rounded. 4. Oblong, which is two to three times longer than broad, with straight, parallel sides. Varieties of this are the linear, which is very narrow and long : when this is rigid and sharp at the apex, it is the needle-shaped leaf; when small and thread-like, it is capillary. 5. Oblique : any of the foregoing forms in which one side has be- come broader than the other; thus, obliquely ovate, obliquely Jieart- shaped, etc. The Base and Apex>—In most leaves two e
. The essentials of botany. Botany. 298 BOTANT. 3. Elliptical, wliicb is longer than broad, lias base and apex equal, and sides rounded. 4. Oblong, which is two to three times longer than broad, with straight, parallel sides. Varieties of this are the linear, which is very narrow and long : when this is rigid and sharp at the apex, it is the needle-shaped leaf; when small and thread-like, it is capillary. 5. Oblique : any of the foregoing forms in which one side has be- come broader than the other; thus, obliquely ovate, obliquely Jieart- shaped, etc. The Base and Apex>—In most leaves two extremities may be dis- tinguished and described. There are three general forms, viz., the acute, obtuse, and notched. (Fig. 192.) The extremity is acute when the approaching sides form an acute angle with each other. When the acute extremity is prolonged, it is acuminate. When the apex ends in a bristle, it is cuspidate. The extremity is obtuse when blunt or rounded. When so blunt as to seem as if cut off, it is truncate, as in what is known as the wedge-shaped {cuneiform) leaf. In some cases a point or bristle grows from the obtuse apex ; such are said to be mucronate. The extremity when indented is notched or emarginate: when this is slight, it is refuse; when so deep from the apex as to appear. Fig. 193.—Diagrams of the principal forms of base and apex. cleft, the leaf is bifid. A common form of emarginate apex is seen in the obcordaie (, inversely heart-shaped) leaf, while the emar- ginate base is found in the cordate (, heart-shaped) leaf. The notch in the base of a leaf is also known as a sinus. Margin of the Blade.—When the growth of the leaf has been uniform throughout, its margin is an even and continuous line, and the blade is said to be entire. More commonly there are inequalities in the growth ; when these are rounded and not great, the margin may be wavy, or if somewhat more, sinuate, which readily passes into the lobed form, with the projections {lob
Size: 2920px × 856px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, booksubjectbotany, bookyear1896
