202 DERMAL AND OTHER NON-VASCULAR TISSUES [CH. 



rhizomes and about the leaf bases in Ferns, while they may be absent from 

 the upper leaves. They attain large size in the Cyatheaceae, where they are 

 borne on massive peg-like outgrowths, which remain as woody spines after 

 the scales themselves have fallen away. This gives a very characteristic 



Fig. 190. Vertical section through the scales covering the rhizome of 

 Phlebodiuin aiireiim, showing their elaborate overlapping. ( x ^^.) 



Fig. 191. Young leaves of Heiiiitelia gra)idifolia, showing 

 broad dermal scales borne on massive emergences, which 

 persist as woody spines after the scales have fallen away, 

 giving the "armature" frequent in Cyatheaceous Ferns. 



"armature" to many species of the family: but it is not constant in them 

 all (Fig. 191). The spines rank as emergences. A very similar condition is 

 found in Gleichenia pectinata : but in place of each broad scale a divergent 

 tuft of stiff hairs is seen, suggesting a primitive state from which the Cya- 

 theoid scale may have originated (Fig. 192). 



