﻿42 2 BOTANICAL GAZETTE [june 



investigated by competent hands, but others which have not will 

 repay thorough study. Only a few notes are here offered. 



Most of the evergreen sclerophyll species examined have a 

 thick, apparently structureless cutinized layer overlying the cells 

 of the upper epidermis. In Rosmarinus officinalis, Pistacia Lentisais, 

 Smilax aspera, and Quercus Ilex, this layer is especially w^ell devel- 

 oped. In the species of the macchie generally the upper epidermis 

 is destitute of stomata. Those checked as thus characterized in 

 the table (p. 4 19) do not by any means exhaust the list, since the 

 leaves of many species were not readily available to the writer 

 for examination. Olea europea, Colutea arborescens, and Viburnum 

 Tt?ms^ occasional members of the Neapolitan macchie, are all 

 destitute of stomata in the upper epidermis. On the other hand, 

 Inula viscosa has many, but its leaves wither in the hottest wea- 

 ther, and they are somewhat protected by a varnish-like cover- 

 ing. SpartiuTfi jtinceum also possesses very small stomata in the 

 epidermis of the upper surface of the leaf, but the leaves are 

 few in number, small, and deciduous in summer. Convolvulus 

 C^ieorum, an undershrub of rare or local occurrence, has many 

 stomata in the upper leaf surface, but these are protected by a 

 dense layer of closely appressed long silky hairs. The case of 

 Thymelaea hirsiita is particularly interesting. It has already been 

 mentioned as an extremely xerophilous plant, and the histology 

 of its leaves throws much light on its power to regulate trans- 

 piration. The leaves are numerous, about 5™"" long by 3™"" wide, 

 somewhat appressed to the branchlets, with the outer surface 

 smooth and shining, the inner surface concave and densely cov- 

 ered with a short, kinky, white pubescence. The branches 

 droop, so that the outer leaf surfaces, which are morphologically 

 the lower or distal ones, are geocentrically the upper surfaces. 

 These contain no stomata, but the concav^e, pubescent inner sur- 

 faces are provided with stomata. The outer epidermis is cov- 

 ered with a cuticular layer, lined with hemispherical cells of a 

 pale yellowish color, apparently containing water stored in the 

 form of a thin mucilage. The next layer is of larger cells, 

 which appear to contain nearly pure water. The mesophyll, 

 which constitutes the main bulk of the leaf, is loose, wnth no 

 well-differentiated layers of tissue. 



