FIBRO-VASCULAR BUNDLES. 



Fid. 40.— Section of a blndo of \ leaf of Festuca rubra. 1 x.TO.— (Hackel.) 



Tlic object iicconiplishod by Ihi^ closinji^ or rolling of tlio leaves 

 is to cover ono Kiirftico jiiul assist in preventing excessive evapora- 

 tion in dry weather. 



The bullifonn cells in their size, number, and arrangement 

 may be used for critical specilio characters. 



Sedges, Cypi'mcw, often have one band of very large bulliform 

 cells in the median line, and nniformly on the up])cr side. 



These modes of arrangement of the bulliform cells is especially 

 important in a i)hysiological point of view, as they produce vari- 

 ous motions of the leaves. 



Fibro-vast'ular Bundles.— In all grasses the structure of 

 these is much the saine. 'I'hei-e are two, rarely four, large i)it- 

 ted vessels, placed side by side near the middle of a bundle, at 

 equal distances from the lower epidermis. The reader Avill hero 

 find it i)rofitable to consult figure 5 for tracing out details. 



Between these is a group of small reticulated cells, as many as 

 fifty in Fesfiicft. anoulliutcea, or only two or three in Panicnm 

 Crns-gaUHhixvw yard grass) and Lccrsidorf/zou/es (rice cut-grass). 

 x\.bove this group, towards the upper side of the leaf, and in a 

 median line of the bundle is one or more annular or spiral ves- 

 sels, situated near an air cavity, made by a breaking away of the 

 veils. 



On the ojiposite si»le, always on a median liiu', is a group of 

 latticed cells or soft bast. 



Surrounding all of the above is the fnnti/Je sheafh formed of 

 long, thick walled c-ells ; and about the whole bundle is the thin- 

 walled i)arenchyma of the fundamental tissue. 



The bundles are not all developed to the same extent. Tiie 



