Anatomie. 659 



xylem of the cotyledon-traces and the rearrangement of the 

 phloem is described as already taking place while in the petiole. 

 The author remarks lipon the difference between this structure 

 and that of the seedling of Peperomla maculosa, where the 

 vascular bundles both in the cotyledons and in the hypocotyl 

 are collateral. D. J. Gwynne-Vaughan. 



LEWTON-BRAIN, L., On the Anatom y of the Leaves of 

 British Grasses. (Transactions of the Linnean Society 

 of London. Ser. 2. Vol. VI. p. 315. PI. 36—40. 1904.) 



The principal object of this paper is to add, by means of 

 diagrams and descriptions of the transverse section of the leaf, 

 to the material at our disposal for the identification of grasses 

 from their vegetative characters. In the first of the three parts 

 into which the paper is divided an account is given of the 

 general anatomy and histology of the grass-leaf, dealing, in parti- 

 cular, with the general outline of its transverse section, the 

 structure of the epidermis, the mesophyl and the vascular 

 bundles, the form and distribution of the „motor cells", stomata, 

 hairs and mechanical tissue. 



In Part 2 the grasses examined (80 in number) are arran- 

 ged for purposes of Classification according to an artificial key 

 based upon the anatomical criteria established in the preceeding 

 part. A short description of the leaf-structure is also given in 

 each case. 



In the third part the leaf-structure of the several grasses 

 is discussed in relation to their habitat. For this purpose they 

 are divided into seven oecological groups. It is demonstrated 

 that in the grasses of 1. meadows and pastures the leaf-struc- 

 ture is not a highly specialized one, and that the group is 

 chiefly distinguished for its negative characteristics. The grasses 

 of 2. waste and sandy places shew but little difference in this 

 respect from the meadow-grasses; not nearly so much as would 

 correspond with the difference in habitat. The leaf-structure 

 of the grasses of 3. woods and shady places is fairly uniform, 

 and is quite well adapted to the less favourable conditions of 

 their habitat for transpiration. The leaves of the grasses of 

 4. maritime sands are strongly xerophytic in structure with 

 abundant stereome, except those that are annuals or possess 

 but short-lived subaerial parts. The grasses of 5. moors and 

 heaths, however, present the most pronouncedly xerophytic 

 structure met with in British grasses. The grasses of 6. wet 

 places shew, in general adaptations favouring effective aeration 

 and transpiration. The leaf-structure of the 7. alpine grasses 

 is less adapted to its environment than that of any of the 

 other groups. They posses none of the characteristic alpine 

 features such as hairiness, smallness, and the one feature 

 they have in common is that they are usually rather thick. 



D. J. Gwynne-Vaughan. 



42* 



