FORJI AND POSITION OF THE TRANSPIRING LEAVES AND BRANCHES. 



343 



a native of the Carpathians, are relatively thin (see figs. 87 * and 87 *). Below the 

 epidermis of the under side is no mantle of bast cells as in the species already 

 described, but only isolated strands of bast; however, the crest of each ridge is 

 furnished with a strand of bast cells; the ridges themselves project very much, and 

 the whole leaf is traversed by six deep narrow grooves. 



In the three fescue-gi-asses cited here as examples, and in all species of the 

 genus Festuca, forming the main part of the turf of our fields, a vascular bundle 



, « -i./??isi 



Wmtf 





AozDcrcr:.- ., 



Fig. 87. — Folding of Grass-leaves. 



1 Vertical section through a closed leaf of Lasiagrostis Calamagrostis. - Vertical section through an open leaf ; x 24. 

 * Vertical section through a portion of the open leaf ; x 210. * Vertical section through a closed leaf of Feaiuca Porcii. 

 « Vertical section through an open leaf; x24. 6 Vertical section through a portion of the open leaf; x210. 



surrounded by green tissue traverses each ridge. In the hinged leaves of many 

 other gi-asses, the green tissue of each ridge is divided into two portions. The 

 vascular bundle is bordered above and below by strands of thick-walled cells devoid 

 of chlorophyll, and thus arises a strong septum in the green parenchyma, beautifully 

 shown in the transverse section of a leaf of Lasiagrostis Calamagrostis, illustrated 

 in fig. 87. In the leaves of the Feather-grass {Stipa capillata) are alternating higher 

 and lower ridges; a vertical section is shown in fig. 86 ^--'^ In the higher ridges 

 occur septa similar to those in Lasiagrostis, but in the lower there is only a vas- 

 cular bundle surrounded by green tissue as in the fescue-grasses. No less than 



