INTRODUCTION 



be familiar with the exquisite colouration of the Horse-Chestnut leaves in 

 the early stages of decay, and the many beautiful gradations through which 

 the leaves of the Elms pass in their change from the sombre green of summer 

 to the golden yellow at their fall. 



In an Oak wood we may see every variety of green and every variety 

 of brown, while among the Beeches we have a long range from modest 

 brown to glowing orange. In the Hedge Maple we find every shade of 

 green, brown, and orange suffused with gold, and among the Brambles and 

 on the Hawthorn we get every possible variation in green, orange, yellow, 

 red, and brown. 



Space will not permit of our going through the list of all our common 

 trees, but we must pause to mention a few of our cultivated trees and 

 shrubs which may be depended on in most years to put on their autumnal 

 livery of crimson, scarlet, and gold. The various species of Maple provide 

 us with examples of red, orange, yellow, and scarlet, and all the species of 

 JEsculus turn yellow. Many of the Thorns (Crataegus) take on brilliant 

 shades of red, bronze, orange, and scarlet, and among the many fine examples 

 of yellows may be placed the Poplars, Sycamore, Tulip Tree, Honey Locust, 

 and Maidenhair Tree. Among shrubs some of the most striking are the 

 Sumachs (Rhus), most of which turn red, while the Barberries furnish us 

 with red, purple, and scarlet. The exact nature of the subtle chemical 

 changes which take place in the cell-contents of the leaf and produce this 

 autumn colouration is not clearly understood, nor is the reason clear as to 

 why it varies so much in different seasons, but, as a rule, it seems to be 

 best when a warm, moist summer is followed by a dry, sunny autumn, and 

 many species colour best when growing in a soil which is not over-rich. 



FLORAL STRUCTURE AND POLLINATION 



Let us for a moment turn our attention to the flowers. We are not 



here concerned with their structure, for that is dealt with fully in the detailed 



descriptions, but we should like to direct the student to the many interest- 



xv c 2 



