APICAL CELL OF PTERIS. 



83 



The funnel-shaped depression is compressed vertically, and its walls are 

 thickly covered with erect branching hairs which are closely fastened 

 together by a hardened mucilage secreted by the apical bud. These hairs 

 entirely close the mouth of the funnel and shut off the delicate young 



FIG. 45. Cross-section of an entire fertile leaflet, m.r, midrib; v, veins; ep, epidermis; 

 ms, mesophyll; sp, sporangia: in, indusium. 



ep. 



FIG. 46. Cross-section, still more enlarged, passing through the midrib of a leaflet. In the 

 centre the circular fibro-vascular bundle, supported, especially above and below, by 

 thickened prosenchyma (p). On either side the parenchymatous. mesophyll cells 

 (shaded) and the intercellular spaces (i.s) opening by stomata (st); epidermis (ep). 



portions at its base from the outer world. Protected by these hairs, the 

 end of the stem forces its way through the toughest clay without injury to 

 the delicate bud buried in its apex. (Hofmeister.) 



