CITAT (MariaS @ 04-08-2009, 08:42)
Då har metasequoyan också blad då.... man sticker sig inte på dem heller!
Fast den är ju definitivt en barrväxt, tillhör ordningen Pinales. Men det förekommer platta , trubbiga barr också.
Gingko har sammanväxta barr som bildar en bladform, men är fortfarande klassad som barrträd. Står om det i de flesta böcker där det går att läsa om just gingkon.
Om barrväxter;
Pines are Conifers with unique Leaf Arrangement.
the pines (Genus Pinus), which include perhaps the most familiar of all gymnosperms dominate broad stretches of North Ameirca and Eurasia and are widly cultivated enven in southern hemisphere. there are about 90 spieces of pines, all of wich are characterized by an arrangement of the
leaves that is unique among living conifers. In pine sedlings the needlelike leaves are spirally arranged and borne single on the stems......
The leaves of Pines, like those of many other conifers, are impressivly suited for growth under conditions where water may be scarce or difficult to obtain. ......A thick cuticle covers the epidermis , beneath which are one more layers of comactly arranged, thick walled cells- the hypodermis. The stomata are sunken below the surface of the leaf. The mesophyll, or ground tissue of the leaf, consist of parenchyma cells with conspicous wall ridges that project into the cells, increasing their surface area (Raven, s 474).
Ginkgo;
The maidenhair tree, Gingko biloba, is easily reconized by its
fan-shaped leaves with their openly branched, dichotomous (forking) pattern of veins. It is an attractive and statly, but slow growing tree wich may reach a height of 30 meters or more. The leaves on teh numerous slowly growing spur, or short, shoots of Ginkgo are more or less entire, whereas those on the long shoots and seedlings are often deeply lobed. Unlike most other gymnosperms,
Ginkgo is decidiuous; its leaves turn a beautiful golden color before falling in autumn (REven s 488).
Ur Raven et al, Biology of plants, sixth edition, Freeman Worth.