280 



PLANTS AND MAN 



All of man's commercially important Angiosperm forest trees 

 belong in the group of Dicots. The Monocots contain no North 

 American tree species of importance from the standpoint of 

 forestry although ornamental species, chiefly the palms and the 

 tree Yuccas, are sometimes used in our southern states. 



Of the twenty four tree genera discussed in the following 

 pages, nine are characterized as catkin bearing plants. Four of 



these, the willows, poplars, birches, 

 and alders have both staminate and 

 pistillate flowers borne in catkins. 

 The walnuts, hickories, beech, chest- 

 nut, and oak, on the other hand, 

 have staminate catkins, but their 

 pistillate flowers are solitary or in 

 short spikes. 



The fifteen genera of non-catkin 

 bearing trees include (7) the elms 

 and red gum, whose flowers lack 

 petals; (2) the ashes and catalpas 

 whose flowers have united petals; 

 and (3) the magnolias, tulip trees, 

 sycamore, cherries, locusts, hollies, 

 basswoods, gums, maples, buckeyes, 

 and dogwoods, whose flowers have 

 separate petals. 



Another method for separation of 



these tree groups is on the basis of 



leaf arrangement. The maples, buck- 



FiG. 198.— Willows have eyes, dogwoods, ashes, and catalpas 



narrow elliptical leaves arranged j^ave opposite leaves; while the Other 



alternately on the stem, and . -, , , , 



small flowers borne in catkins, ^meteen have leaves alternately 



arranged on the twigs. In the follow- 

 ing paragraphs, alternate leaved catkin bearing trees are first 

 considered, followed by the alternate leaved, and finally opposite 

 leaved, non-catkin bearing trees. 



The Willows 



The v^LLOWS {Salix) have alternate, pointed and elliptical 

 leaves. There are no true terminal buds on the branches; the 



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