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narrow, erect wings, continuous along the rachis or along 

 the rachis and stipe opening laterally at the insertions 

 of the pinnae. An effect similar to that of the winged 

 stipe is produced by the auricles of the pinnae of some 

 species standing close to, or against, the rachis and each 

 underlying the base of succeeding pinnae. Nephrolepis 

 cordifolia is an illustration. The convexity of the major 

 areolae of Polypodium afline and P. heracleum can con- 

 duct water along the main veins and costae just as a 

 wing, convex as a whole does, and the rows of close- 

 set papillae on the segments of P. papillosum must oper- 

 ate in the same way. 



Irrespective of the ease or difficulty of becoming wet 

 (as a matter of fact, for a reason which I shall pres- 

 ently develop, cut, incised and dissected fronds shed 

 water), finely dissected fronds dry readily by evapora- 

 tion. There are two reasons for this : the limited single 

 surfaces preventing the holding of much water, and the 

 ready agitation brought about by movements of air. 

 Aside from these general adaptations to promote the 

 facile escape of water from a frond, there are various 

 other devices which prevent the passage of water to its 

 nether surface. A very simple structure of this kind is 

 the convexity of the ultimate divisions of the frond, such 

 as that of the segments of Blechnum egregium and the 

 ultimate pinnules of Nephr odium setigerum. To reach 

 the nether surface of any of these structures, water would 

 have to run up-hill from the margin. This is equally the 

 case when the margin of an otherwise plane frond or 

 division is deflexed, as in Antrophium plantagineum, 

 Polypodium punctatum and Acrostichum. In the major- 

 ity of these plants the margin is sharp as well as deflexed. 

 A few species have a sharp margin which is not deflexed. 

 The sharpness alone must prevent a drop of water from 

 running to the nether surface. If the entire surface is 

 wet, the water need not perhaps move in drops, but 

 might move in a film around even a sharp edge, but so 



