IV ON PLANT LIFE 149 



In illustration of the first case I may refer 

 to many alpine plants, the well-known Edel- 

 weiss, for instance, where the woolly covering 

 of hairs prevents the " stomata," or minute 

 pores leading into the interior of the leaf, 

 from being clogged up by rain, dew, or fog, 

 and thus enable them to fulfil their functions 

 as soon as the sun comes out. 



As regards the second case many desert and 

 steppe-plants are covered with felty hairs, 

 which serve to prevent too rapid evaporation 

 and consequent loss of moisture. 



The woolly hairy leaves of the Mulleins 

 (Verbascum) doubtless tend to protect them 

 from being eaten, as also do the spines of 

 Thistles, and those of Hollies, which, be it 

 remarked, gradually disappear on the upper 

 leaves which browsing quadrupeds cannot 

 reach. 



I have already alluded to the various ways 

 in which flowers are adapted to fertilisation 

 by insects. But Ants and other small creep- 

 ing insects cannot effectually secure this object. 

 Hence it is important that they should be ex- 

 cluded, and not allowed to carry off the honey, 



