. Un libro di botanica per scuole e università ... La botanica. 646 Ecologia woody, stelo perenne, di solito con un singolo trunk principale; un shruh possiede una simile ma più piccolo stelo, solitamente mth un numero di approxi- valgono pari i turioni derivanti in corrispondenza o vicino alla base; un'erba non è costitui- spicuously woody e di solito ha un annuale dello stelo antenna e spesso anche un perenne dello stelo della metropolitana. Questi dis- tinctions, tuttavia, sono arbitrari, gradazioni tra alberi e arbusti essendo comune; erbe e arbusti intergrade anche, specialmente nei tropichi, dove tutti i gradi di woodi- ness esistono e dove herbaceou

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. A textbook of botany for colleges and universities ... Botany. 646 ECOLOGY woody, perennial stem, usually with a single primary trunk; a shruh possesses a similar but smaller stem, usually mth a number of approxi- mately equal shoots arising at or near the base; an herb is not con- spicuously woody and usually has an annual aerial stem and often also a perennial underground stem. These dis- tinctions, however, are arbitrary, gradations between trees and shrubs being common; herbs and shrubs also intergrade, especially in the tropics, where all degrees of woodi- ness exist and where herbaceous stems often endure for two or more years. Herbs may be subdivided further into forms whose stems are wholly subterranean (as in many ferns), forms whose stems are wholly aerial (as in annuals), forms which have both aerial and subterranean stems (as in most peren- nials), and forms which apparently are stemless (as in some rosette plants). The display of foliage leaves by steins. — Elongation and branching.—From the stand- point of the maximum display of foliage to light and air, the most significant stem features are elongation, branching, and erectness. Elon- gation is a char- acteristic feature of most aerial stems, though it is lacking in various rosette plants; growth in height proceeds with extreme slowness in certain other cases, particularly in the cycads, some of which are said to require centuries to reach a height of two or three meters. Branching is relatively slight in the pterido- phytes, cycads, and monocotyls (fig. 951), reaching its culmination in. Figs. 952, 953. — Twigs of a maple {Acer): — 952, a termi- nal twig in its natural position; note the erect terminal bud (6) of the main shoot, all other buds being ascending rather than erect, whether they are the terminal buds {b') of lateral shoots or the lateral buds (i") of the main shoot; i, bud scales; note that the terminal buds are larger than the lateral buds; 953, a horizontal twig in its na

Parole chiave associate all'immagine

• bookcentury1900
• bookdecade1910
• booksubjectbotany
• bookyear1910