Transactions of the Royal Society of New Zealand . th leaf * 356 Transactions. There is a clear indication that the leaf-trace bundles are sent inwards. The Root.—The stele is diarch; the bundles of phloem are quite distinctand easily distinguished from the xylem. As in the majority of roots, themedulla becomes obliterated. In old roots the structure resembles that of the stems, in that secondaryxylem and phloem are developed from an extra-fascicular cambium. Itdiffers in that phloem islands in the root are slightly larger than those inthe stem, and the fibrous cells round them have thi
Transactions of the Royal Society of New Zealand . th leaf * 356 Transactions. There is a clear indication that the leaf-trace bundles are sent inwards. The Root.—The stele is diarch; the bundles of phloem are quite distinctand easily distinguished from the xylem. As in the majority of roots, themedulla becomes obliterated. In old roots the structure resembles that of the stems, in that secondaryxylem and phloem are developed from an extra-fascicular cambium. Itdiffers in that phloem islands in the root are slightly larger than those inthe stem, and the fibrous cells round them have thinner walls. The dis-tinction between one seasons growth and the next is more apparent. A cross-section of the hypocotyl shows two groups of xylem whichconverge to form, in the root, the plate, on each side of which is the phloemgroup (see fig. 5, a). The development of the root takes place as usual. Seedlings have numerous long delicate hairs, the outline of which isoften crinkled and wavy. They present a curious resemblance to fungal b c Xylem. Rootlet -a, Transverse section of root of an old plant; b, transverse section of youngbranch, near tip ; c, transverse section of part of internal structure of rootof a seedling. hyphae, and portions of them are often swollen, especially the tip. Someof them are as much as 2 mm. in length, while the root is only 0-25 diameter. They extend along the root, from just behind the growing-point to the base of the hypocotyl. Cotyledons.—Stomata occur on the upper and lower surfaces, and areplaced as in leaf and leaf-base, but are not sunk beneath the guard-cells are short and wide, so that in surface view the stomataappear circular. Epidermis.—Surface view of epidermal cells shows that they are wavyin outline. In a cross-section the radial walls are shorter than the tan-gential, and the outer walls are flat. Seedlings grown in a greenhouseshowed chloroplasts, few in number, in some of the epidermal cells. In cotyledon
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectscience, bookyear1911
