FliTUHK JioTAMST. 13 



or by ail expanded leai'-stalk. Stipules are iiiolialily useful in 

 other ways, c.y., in conducting' rain down tlie stem. 



Hairs are found very commonly in Nature, tiiul are used for 

 all soils of [jurposes. The most important is probably to guard 

 against excessive loss of water by transpiration. In the Sahara 

 Desert the prevailing- tint of the landscape is grey, not green as in 

 our own country, because almost all the shrubs are covered with 

 grey and silvery hairs. This also occurs in Europe in exposed 

 situations. The Edelweiss growing' on wind-swept rock ledges 

 is densely white and silvery, so is the .Vlpiiie Ladies' Mantle. 

 These plants cover themselves with cotton-wool to keep the 

 moisture in just as we use clothes to keej) the rain out. An 

 instance of this is found in our Alpine duckweed, found at 

 Black's Hope, &c. This chiefly differs from the common species 

 by being' more woolly and having' larger flowers. AVe can in this 

 case g'uess how this species may have arisen, for a variety 

 (alpestre) of the common c. triviale, which I found to be common 

 (111 Whitcuomb and Auchencat in 18'.)2, is both more hairy and 

 larger flowered than is usual, and so approaches the Alpine form. 

 There is even a good deal of evidence on hand to sho^v that hairs 

 disappear when such exposed plants are cultivated in moist and 

 slielti'red places. I have found this myself in a desert plant which 

 1 grew in a g'reenliouse, and which lost its hairs in that situati(jn. 

 Something- of the same kind is found in Polyg-onuui Amphibium, of 

 which laud forms are viscous and hairy, while water forms are quite 

 smooth. In tliis species the hairs are probably of use in guarding- 

 against insects. It is said that hau's occasionally absorb moisture. 

 1 )ut this cannot be considered proved. I have already alluded to their 

 USB as protection ag-ainst insects ; a good example is the character- 

 istic downward-pointing hairs of the Forget-me-not. The sting- 

 ing hairs of the nettle prevent human beings from injuring its 

 brittle stems, and the hairs of the white deadnettle, as well as the 

 plant generally, are so similar that the latter enjoys the same pro- 

 tection. In other cases they are utilized for climbing- or the dis- 

 tribution of seeds, as, e.//., in the goose grass and other Galiums. 

 The Sundew uses modified hairs to catch insects. In the Chick- 

 weed they are used to conduct water down the stem, and so on. 



Tile modifications of the stem are scarcely so well known ; 

 plants are annual and perennial as a matter (jf convenience;. The 

 toriuer are most common where there is a distinct check to veu'e- 



