14 Some Aspects of Plant- Life. [Sess. 



drought, the reason being that plunging the pot in water 

 excludes air from the soil, and the normal activities of the 

 plant cannot go on, transpiration amongst others. Hence the 

 plant is in the position of the mariners who had " Water, water, 

 everywhere, Nor any drop to drink." 



Among adaptations to rather dry situations one may notice 

 water-receptacles formed by the leaves of teasels and silphiums. 

 Some bromeliads have similar water-cups, but in their case 

 the water gathered forms a trap for the bodies of insects, and 

 so affords an extra food-supply to the plant by means of the 

 nitrogenous material absorbed from the insects' bodies. 



Some plants suffer from lack of water, others have too 

 copious a supply. In the latter case deeply sunken midribs 

 with " drip tips " may help to run off the surplus, or holes 

 more or less regularly placed along the leaf may let much of 

 the continually dripping moisture run through. 



Some leaves reduce their transpiration surface by rolling up 

 and drooping together. This was well seen in rhododendrons 

 during the frost of the winter of 1894-95. Many a gardener's 

 summer is spoiled by brilliant sunshine in spring while the 

 ground is still cold or even frozen. 



Coming to a closer study of the adaptations we have been 

 considering, we recall the reduced leaf-surface of such plants 

 as the broom and gorse, with the lessened transpiration that 

 such reduction entails, the long leafless internodes still further 

 reducing transpiring surfaces, the thickened epidermis, and 

 deeply-sunk stomata or breathing-pores. In some cases these 

 stomata are fringed with interlacing hairs, thus enclosing a 

 layer of still and moist air, and guard-cells surrounding the 

 stomata automatically close the outlets when turgescence is 

 lessened owing to drought, and so stop transpiration altogether 

 •or reduce it to a minimum. 



Mistletoe, holly, and oleander present good examples of the 

 thickened and stratified cuticle found in plants adapted to 

 withstand drought well. 



Other adaptations similarly useful are the placing of the 

 stomata in pit-like depressions, and the presence of hairs of 

 peculiar shape, which cover the epidermis of the leaf with a 

 protective layer, enclosing in its meshes a body of moist still 

 air not readily removed. Such hairs may be floccose or 



