306 ANATOMY OF LEAVES. 



ami nation of a portion of the cutis of any leaf. Ad- 

 mitting these lines to be lymphatic vessels, it is not 

 improbable, as Kieser has asserted, that they termi- 

 nate by one extremity in the larger vascular fasciculi. 

 The meshes which they form, differ very much, both 

 in form and size, in different leaves. In almost all 

 the monocotyledons, in the Grasses, and in every 

 plant the leaves of which have parallel costae, the 

 meshes are nearly irregular parellograms ; but, in 

 forming these, the vessels sometimes run in straight 

 lines, as in common Meadow Grass (Poa triviaUs) ; 

 sometimes in slightly undulated lines, as in the White 

 Lily ; and sometimes zigzag, as in Indian Corn. In 

 some of the fleshy leaves they are nearly regular hexa- 

 gons, as on the upper disk oiHoija carnosa, and on both 

 surfaces of the leaves oiAloe ver?-ucosa: but, in the ma- 

 jority of dicotyledons, they assume very irregular fig- 

 ures. Whatever may be the fissures which they pre- 

 sent in the cutis covering the spaces between the 

 vascular ramifications of the leaf, they invariably ap- 

 pear as irregular parallelograms in that which covers 

 the vascular fasciculi ; a fact which gives some sup- 

 port to the opinion of Kieser, that the vessels forming 

 the meshes terminate in these fasciculi. The differ- 

 ence in the size of the meshes, in different leaves, is 

 still more striking than in their forms ; but in all they 

 are very minute. On a portion of the cutis of Aloe 

 verrucosa, -g^-g of a square inch in size, Mr. Thompson 

 counted 96 meshes, or 55 yWo to the square inch ! 



The form of the cuticular cells, owing to the cutis 

 being more transparent than the epidermis which cov- 

 ers it, can be demonstrated only as they appear in a 

 vertical section. They are either spheroidal or oval ; 

 and are found generally empty, or filled with a colorless 

 fluid. In the greater number of leaves the cutis con- 

 tains one layer only of cells ; but it may contain sev- 



