456 MESSRS. J. PARKIN AND H. H. W. PEARSON ON THE 
chlorophyll, although their likeness to the plastids of the meso- 
phyll render it highly probable. Solereder * mentions species 
of the order Scrophulariacew, but not Gesneracex, to which 
Didymocarpus belongs, as having chloroplasts in their epidermis. 
Neither of the above plants shows marked xerophytic characters 
in the leaf. In fact, Didymocarpus Humboldtiana is decidedly 
mesophytic in structure ; it grows on wet boulders. Pedicularis 
zeylanica has its outer epidermal walls somewhat thickened and 
possesses fairly well differentiated palisade-cells. 
VIII. Appirionat Points oF ANATOMICAL AND 
PuysioLoaicaL INTEREST. 
In this division of the paper are included certain features 
of interest. bought to light during the microscopic examination 
of these plants, which, however, have hardly any cecological 
bearing, but which, we think, are worth recording. Several of 
them require further investigation. 
(1) Zannin Idioblasts in the Mesophyll.—Distributed in the 
mesophyll of several of these plants are special sacs, which in 
the alcoholic material are coloured brown and which are usually 
larger than the ordinary chlorophyll-cells. They may have a 
scattered arrangement, or be located chiefly in the palisade- 
tissue, or form a more or less definite layer in the middle of the 
leaf, or be aggregated mainly round the fibrovascular bundles. 
Solereder + refers to such cells as tannin idioblasts, and mentions 
them as being of common occurrence in the Sapindace®, Papilio- 
nacew, Mimosew, and Rubiacex. The brown coloration possibly 
arises from the action of an oxidase on the tannin substance, 
changing it into a phlobaphene or some kindred body on the 
death of the cell. 
Their occurrence has been noticed in the mesophyll of the 
following patana plants :-— 
Papilionacew.—Atylosia rugosa (Pl. 12. fig. 3, ¢s.), Tephrosia 
tinctoria. . 
Rubiacexw. — Canthium parviflorum, C. Rheedii, Hedyotis 
Lawsonie (Pl. 11. fig. 2, ts.), Knowia platycarpa Vv 
hirsuta, Mussenda frondosa (P\. 11. fig. 10, ts). 
Polygonacew.— Polygonum chinense. 
* Solereder, Syst. Anat. Dicot. (1899) p. 907, for list of natural orders 
with chloroplasts in epidermis. 
t olereder, 2, ¢. p, 924. 
