360 Mr Corry, On some points in the structure, etc. [Ap. 30, 



Adult Appearance. 



Since MacNab 1 has recently laid stress upon the features 

 exhibited by the leaves in transverse section as a guide for the 

 determination of species and genera, a brief resume of the charac- 

 ters presented by those of P. silvestris is appended. 



Leaf about twice as broad as it is thick, upper surface flat, lower 

 convex. Epidermis possesses stomata in rows on both surfaces 

 though they are most frequent in the convex surface. 



Hypoderma conspicuous, forming a single or double layer 

 around the whole periphery of the leaf, broken only immediately 

 below the stomata. 



Palisade tissue presents no apparent differences on the upper 

 and under surfaces. All the cells closely packed, being 2 — 3 rows 

 deep, forming a continuous zone surrounding the medullary tissue ; 

 there is no spongy tissue. The intercellular spaces are only due to 

 the formation of pseudo-intrusive ingrowths, and their number is 

 not great in proportion to the leaf. These cells contain chlorophyll. 



Resin Canals, two large and constantly present, viz. one at each 

 angle of the leaf near the margin, not far from the epidermis ; one 

 smaller unpaired median one usually present in the centre of the 

 upper surface. 



Medullary parenchyma, several layers of cells closely packed 

 without chlorophyll and with conspicuous bordered pits ; outer 

 layer of short cubical cells, forming well-marked sheath to the 

 fibrovascular bundle. 



Fibrovascular bundle, single with two distinct branches, sepa- 

 rated by a certain amount of medullary parenchyma forming a 

 primary medullary ray, usually a few greatly-thickened scleren- 

 chymatous cells above and below the bundle. No bast fibres. 



May 14, 1883. 



Mr Glaisher, President, in the chair. 



At the Meeting of the Cambridge Philosophical Society held 

 on Monday, May 14, Mr F. Darwin, M.A., Trinity College, was 

 ballotted for and duly elected a fellow of the Society. 



1 "A Revision of the Species of Abies," Proceedings of the Royal Irish Academy, 

 Ser. ii. Vol. ii. Science, pp. 673 — 704. 



