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Transactions. 



The ground-tissue consists of large, rounded, thin-walled, closely arranged 

 cells. The 1-2 layers of these cells adjacent to the epidermis are chloren- 

 chymatous, as also in the tissue in the margin of the petiole. The main 

 bulk of the ground-tissue is, however, colourless, forming an aqueous tissue. 



Rhizome (fig. 29). — The epidermis consists of cells which are oval or 

 rounded in transverse section, and which have all their walls slightly 

 thickened, the external being the most thickened. A very thin, uneven, 

 ridged cuticle is present. The cortex consists of large, rounded, colourless 

 cells which have their walls slightly thickened and which form a water- 

 storage tissue. In the inner part of the cortex there are, at intervals, a few 

 secretion-canals which are lined with a layer of thin-walled epithelial cells. 



Fig. 28. — Brachycome Sindairii. Transverse section of petiole (x 72). 

 a, unicellular hair ; b, chlorenchyma ; c, aqueous tissue ; 

 d, xylem ; e, phloem. 



The endodermis is well marked, consisting of a layer of irregular cells 

 with thin suberized walls. There is no continuous pericycle, but this layer 

 is represented by a number of groups of pericycle fibres, in which the cells 

 have thick, lignified walls and small lumen. The phloem forms a fairly 

 wide band and is continuous round the xylem ; it consists of sieve-tubes, 

 companion cells, and a fairly large amount of phloem parenchyma. The 

 xylem joins a practically continuous band of vessels and of wood-fibres 

 with fairly thick walls. It is interrupted by a few uniseriate medullary 

 rays, also with thickened, lignified walls. The pith is solid, and consists 

 of thin-walled, large, round cells. 



In an older part of the rhizome the epidermis has disappeared, and the 

 outer layer of the cortex is suberized. 



