386 LEAF-ANATOMY OF THE GENUS ANDROPOGON, 



differentiation. The methods adopted, in embedding and mount- 

 ing, were similar to those used in ordinary microtechnique. 



Andropogox intermedius R.Br. (Plate xxx.). 



In the widest portion of the leaf, there are nine primary 

 bundles, i.e., bundles in which the sclerenchyma is in direct con- 

 tact with the phloem or xylem, or separated from the latter by 

 thin-walled cells only. The primary bundle of the midrib is the 

 largest. There are 33 secondary bundles, i.e., bundles in which 

 phloem and xylem are completely surrounded by chlorophyll- 

 bearing cells. 'I'here are also present six bundles of an inter- 

 mediate type. In these bundles, the sclerenchyma is developed 

 under the bundle, but separated from the phloem and xylem of 

 the bundle. The primary bundles are surrounded by thick- 

 walled cells — the mestome sheath. On the outer side of these 

 are thin-walled parenchyma-cells which, in this case, are very 

 indistinct. 



Midrib. — In the widest portion of the midrib there are three 

 primary bundles, and these are open above and below. The 

 chlorophyll-bearing parenchyma-cells, surrounding the middle 

 bundle, are smaller than those surrounding the mestome bundles. 

 The sclerenchyma on the lower surface of the midrib is well 

 developed, but that on the upper surface consists of but few cells, 

 which are in direct contact with the epidermal cells. 1~he scler- 

 enchyma on the superior surface of the other two primary 

 bundles is much better developed than that of the middle primary 

 bundle. The phloem tissue is extremely well developed in all 

 the primary bundles, and this also applies to the xylem tissue. 

 Xylem and phloem tissue are also developed in the secondary 

 bundles, the former preponderating. 



The epidermal cells on the lower surface are extremely irregular 

 in size. The cuticle, by which they are protected, is not par- 

 ticularly thick, except over the primary bundles, and at the 

 edges of the leaf. The epidermal cells on the upper surface are 

 as small as those on the lower surface only under the secondary 

 bundles. In all other cases, they are considerably extended in 

 size, penetrating deeply into the mesophyll-tissue. These cells. 



