254 TRANSACTIONS OF THE [Sess. lxxvii. 



adaptations to be met with among plants of dry areas 

 generally, no matter whether these are regions of : — 



(1) Deficient rainfall. 



(2) A substratum unretentive of moisture, such as rocks 



or sand or shingle. 



(3) Extreme exposure to sun and wind. 



(4) Saline soils inhibiting absorption. 



Water Storage. — Succulent plants which store their water- 

 supply in thick fleshy leaves, and sometimes also in a fleshy 

 stem, are well represented by Suaeda maritima, Dumort. ; 

 Spergularia media, Pers. ; Glaux maritima, Linn. ; Sedum, 

 anglicum, Huds. ; Cochlearia officinalis, Linn. ; Atriplex 

 patula, Linn. ; and Aster Tripolium, Linn. 



Reduction of transpiration surface is seen in the narrow 

 linear leaves of Armeria maritima, Willd. ; Sagina pro- 

 ■cumbens, Linn.; Triglochvn maritimum, Linn.; and 

 Plantago maritima, Linn.; and in the setaceous leaves 

 of Festuca ovina, Linn. ; and Nardus stricta, Linn. The 

 bi-pinnatifid leaves of Matricaria inodora, Linn., have 

 segments which are so much reduced that the entire 

 surface is not of great extent ; while the small ovoid leaves 

 of Sedum anglicum, Huds., and the cylindrical ones of 

 Suaeda maritima, Dumort., and Spergularia media, 

 Pers., exhibit the minimum surface area compatible with 

 their increased water-storing capacity. 



Protection of transpiration surface is instanced in the 

 dense woolly covering to the under surface of the leaves 

 of Tussilago Farfara, Linn., and Artemisia vulgaris, 

 Linn. ; as well as by the silky hairs on those of Potent ilia 

 anserina, Linn. ; and in the more general hairy covering 

 of Scutellaria galericulata, Linn. The device of inrolling 

 of leaf -blades is found in Glyceria maritima, Wahlb. 



Compact or Creeping Habit. — Many of the plants named 

 are of those types which avoid undue exposure to the 

 drying and destructive action of the wind by means of 

 their habit of growth. Stellaria media, Vill., and Gcdium 

 Aparine, Linn., for instance, creep close to the surface, 

 availing themselves of what little shelter is afforded by the 

 association of which they form a part. Sagina pro- 

 cumbens, Linn., clings close to the rocks, while the cushion- 

 growths of Armeria maritima, Willd., and Grimmia 



