564 



Transactions. 



The central cylinder is of a rather anomalous character. There is a 

 well-marked endodermis, beneath which are 2-3 layers of thin-walled cells, 

 followed by bead-like rows of cells ; and these in all cases were found to 

 contain green chromatophores, which seems very remarkable in such a deeply 

 seated tissue. Next are 2-3 layers of thin-walled cells, evidently an extra- 

 fascicular cambium such as De Bary describes in S. herhacea ; and on the 

 inner side of this cambium ring, and evidently formed from it, is a zone cf 

 xylem, enclosing a pith containing the original collateral bundles. In the 

 centre is a small medullary cavity. 



9. Spergularia media. 

 Leaj. 



Epidermis (fig. 12, &) consists of cells with wavy outline, the cuticle 

 being thin, but marked with fine striations. Stomata are rather numerous 

 on both surfaces. Peculiar hairs terminated by rounded knobs perhaps 

 function as hydathodes (fig. 12, c). 



Mesophyll : (a.) On the upper side are 4 layers of palisadic cells with 

 numerous chlorophyll grains : some contain masses of crystals ; some 

 contain anthocyan, though this is not present in the' epidermis, (b.) Colour- 

 less parenchyma of thin-walled cells, polygonal, or somewhat rounded in 



3torrha, 



Fig. 12. — Spergularia media. 

 a. T.S. leaf, X 32. h. Surface-view of epidermis of leaf. c. Hair from leaf. 



outline, with few and small intercellular spaces ; in some cases this occupies 

 about half the width of the leaf and more than one-third of its thickness ; 

 masses of crystals are found here also. 



The midrib has a well-marked sheath. The xylom is very prominent, 

 but there is little phloem. The v.hole is embedded in a mass of scleren- 

 chvma. 



