EQUISETUM. SPOKOPHORE. 219 



3. The bulky parenchyma with numerous starch grains : 

 there are no large intercellular cavities as in the aerial axis. 



4. Isolated vascular bundles, each of which is surrounded 

 by a special bundle-sheath, quite distinct from that of the 

 other bundles ; there is no general bundle-sheath as in the 

 normal axes. 



A comparison of the stems of various species of Equisetum in 

 respect of the bundle-sheath shows that there is some want of 

 uniformity in its arrangement, even in the normal axes : further, 

 it has been shown that such differences may occur between the 

 rhizome and the aerial axis even in the same species. In 

 E. arvense there is a difference in this respect between the 

 tubers and other axes. 



VI. Make preparations suitable for the study of the 

 epidermis in surface view, by cutting longitudinal, tan- 

 gential sections, and treat as before, mounting with 

 the outer surface uppermost : observe under a high 

 power 



,1. That the superficial cells covering the ridges are of 

 elongated form, with smooth outer walls, and thickened, 

 pitted, inner walls : there are no stomata on the ridges. 



2. That the superficial cells of the grooves are 

 shorter, and nearly square, their outer walls bearing 

 those rounded excrescences already observed in trans- 

 verse sections, while their whole surface is dotted with 

 small projections : in this part are also numerous 

 Stomata, which present the characteristic appearance 

 of two > concentric circles, the outer being the limit of 

 the two subsidiary cells, the inner that of the two 

 guard-cells. Note also the peculiar radiate marking, 

 which is due to irregularity of thickening of the wall 

 separating the guard-cells from the subsidiary cells. 



Treat sections similar to the above with Schulze's macerating fluid 

 (KCl 3 + HN0 3 ) for some hours, and then dry them with 



