Trees; a handbook of forest-botany for the woodlands and the laboratory . Fig. 16. Leaf of Chestnut, Castanea vesca, showing strict-pinnatevenation. The tertiaries break up rapidly into the reticulation (Ett). The following afford examples of strict-pinnate vena- tion Horse-chestnut Chestnut Hazel Hornbeam Elms White Beam Alder Birch Beech. v] PINNATE-LOOPED VENATION 57 A third form of pinnate venation may be distinguishedas follows. The single midrib gives off pinnate second-. Fig. 17. Leaflet of Walnut, Juglans regia, showing pinnate-loopedvenation. The secondary ribs b leave the midrib a in
Trees; a handbook of forest-botany for the woodlands and the laboratory . Fig. 16. Leaf of Chestnut, Castanea vesca, showing strict-pinnatevenation. The tertiaries break up rapidly into the reticulation (Ett). The following afford examples of strict-pinnate vena- tion Horse-chestnut Chestnut Hazel Hornbeam Elms White Beam Alder Birch Beech. v] PINNATE-LOOPED VENATION 57 A third form of pinnate venation may be distinguishedas follows. The single midrib gives off pinnate second-. Fig. 17. Leaflet of Walnut, Juglans regia, showing pinnate-loopedvenation. The secondary ribs b leave the midrib a in pinnate order,but curve forwards (near d and e) and loop with the next in front. Inthis case the looping is so near the margin that an infra-marginal veinmay result, c tertiaries, forming cross-ties and breaking up into thenetwork (Ett). 58 PINNATE-ARCUATE VENATION [CH. aries, which do not end in the margin, but take a sinuousor curved, or more rarely straight, course, and then bendforwards at their tips and join in a loop, convex to themargin, with the next upward secondary (Fig. 17). Wemay term this pinnate-looped venation. The following afford examples of pinnate-looped vena-tion :— WalnutRobiniaSpindle TreeAppleHoneysuckle. Travellers Joy Ailanthus Rose Sweet-briar Lilac Holly Blackthorn Alder Buckthorn
Size: 1300px × 1923px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, bookidtreeshandboo, bookyear1904
