604 THK STEMS OF CLIMBING PLANTS, 



those of the pith. Outside the bast is a ring of sclerenchymatous 

 cells, that apparently acts as an endoderniis also, The bark 

 shows all the usual tissues excellently — phelloderm, phellugen, 

 cork, and epidermis with cutin. Scattered, sclerenchymatous 

 elements are found also in the circumferential parts of the pith. 



•2. Chiastoxylon. 



(a.) BiGNONiA TwEEDiANA Lindl., (Plate Ixi., fig 4).— In trans- 

 verse section, the pith is roughly square in outline, and a rect- 

 angular ray of bast strikes the centre of each side of the square 

 at right angles or nearly so. From the inner end of each bast 

 ray, a small cone of wood (protoxylem) penetrates the pith to 

 about one-sixth of its diameter. The pith-cells are filled with 

 starch-grains. The wood is continuous round the pith, but forms 

 a very narrow connecting band at the base of each bast-ray, near 

 the protoxylem-masses already mentioned. The vessels occur in 

 V-shaped bands, which are most definite near the bast. The 

 wood-parenchyma forms irregular, radiate rows. The bast-rays 

 project into the cortex at their circumferential limit, and pre- 

 serve their shape as rectangular masses. Their bast consists of 

 alternating strips of hard and soft bast, the latter of more rows 

 of elements. The bast rays are connected by a bast-ring sur- 

 rounding the four masses of wood, and showing alternate strips 

 of hard and soft bast, as in the rays. There is an incomplete 

 circle of sclerenchyma within the phellogen, beyond which are 

 6-7 tiers of cork-cells bounded by dead bark. 



[b.) BiGNONiA PiCTA Lindl., (Plate Ixii., fig.oj. — The bastforms 

 four square masses of five thin layers of hard bast, alternating 

 with five broader layers of soft bast. Where these masses occur, 

 the wood-tissues have about half their usual depth, and press on 

 the central pith, giving it almost a square outline. The cambium 

 is thick and definite. It is depressed at each of the bast-patches, 

 so that the cambium-ring has a crenulated outline. On a circle 

 outside the bast are a number of roughly elliptical masses of 

 thick-walled sclerenchyma. A second narrow and almost com- 

 plete ring of sclerenchyma, bounding the cork-cambium, is 

 constructed of brick-shaped cells, whose cavities are almost 

 obliterated. 



