The Encyclopaedia Britannica; .. A dictionary of arts, sciences and general literature . proximated so as to form as it were one, and then severalleaves may be produced at the same height on the . two leaves are thus produced, one on each side ofthe stem or axis, and at the same level, they are calledopposite (fig. 126); when more than two are produced(fig. 127), they are verticillate, and the circle of leaves isthen called a verticil or whorl. When the zone of the axiswhich produces the circle of leaves ia transverse from itsorigin, the whorl is a true one; but when the zone is there
The Encyclopaedia Britannica; .. A dictionary of arts, sciences and general literature . proximated so as to form as it were one, and then severalleaves may be produced at the same height on the . two leaves are thus produced, one on each side ofthe stem or axis, and at the same level, they are calledopposite (fig. 126); when more than two are produced(fig. 127), they are verticillate, and the circle of leaves isthen called a verticil or whorl. When the zone of the axiswhich produces the circle of leaves ia transverse from itsorigin, the whorl is a true one; but when the zone is theresult of unequal development or of displacement the whorlis spurious. Again, in each whorl the leaves may be all 116 B O T A N r [jJOTEITIVE 0BCAK8, formed together, and a simultaneous whorl results ; or theymay be formed one after the other, as m Characeas, whena successive whorl is formed. When leaves are opposite,each successive pair may be placed at right angles to thepair immediately preceding. They are then said to decus-sate, following thus a law of alternation. The same occurs. Fig. 126. F«- 128. Tia 126.—A stem \rith opposite leaves. The pairs are placed at right angles alter-nately, or In what Is called a decussate manner. In the lowest pair one leaf IsIn front, and the other at the bacli; In the second pair the leaves arc placedlaterally, and so on. Fia. 127.—Vertlclllate or whorled leaves of a species of Madder. There are Aveleaves In the verticil or whorl. Flo. 128.—A stem with alternate Itaves. arranged In a pentastlctious or qulncnn-clal manner. The sixth leaf la directly above the flrst, and commences thesecond cycle. The fraction of the circumference of the stem expressing thedivergence of the leaves is two-fifths. in the verticillate arrangement, the leaves of each whorl rarelybeing superposed on those of the vrhorl next it, as on thebranches of Chara, but usually alternating so that each leafin a whorl occupies the space between two leaves of thewhorl n
Size: 1866px × 1339px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, booksubjectencyclo, bookyear1902
