those which stand on the stem at such an angle as to 

 expose the under side to the rays of the sun. Under 

 any or all of these conditions, the coating may serve as 

 protection against rapid changes of temperature, or me- 

 chanical injury from insects or from plant parasites. 



This function of protection in some one or all of 

 these various ways, is too well substantiated to require 

 any farther proof. The possibility of another, perhaps 

 equally important one, by which the hair may contribute 

 actively to the supply of water for the use of the plant, 

 as well as merely to prevent the escape of that taken 

 up by the root-hairs, suggested the anatomical study of 

 the various kinds of Filz in reference to this point. 



The great variety in form of Trichomes and their 

 probable physiological meaning has long been the subject 

 of thorough and patient investigation. The literature on 

 this subject is too well known and too far-reaching to 

 render a formal statement of it of any particular value 

 in this connection, except it may be a brief reference 

 to several more recent articles which have a special 

 bearing on this point. 



Among these is „Die Anpassung der Pflanzen an 

 Regen und Thau" von Axel L. Lundstrom, Docenten 

 der Botanik an der Universitat Upsala, 1883. The object 

 of this article as the name implies, is to show that the 

 higher laud plants have peculiar arrangements to enable 

 them to make use of the moisture contained in the atmo- 

 sphere and that received direct from the rain-falls. A 

 large number of plants were studied with special reference 

 to such peculiarities of structure as are usually considered 

 accidental and which have hitherto been passed by, 

 or overlooked, as destitute of any physiological interest. 



