THE THEE. 5 



growing on dry, gravelly soil had a tap-root that was 

 evidently twenty feet long, while on moist fertile clay 

 land in the same section such trees probably seldom have 

 tap-roots more than six feet long. 



Buds are placed regularly on the young branches and are 

 said to be either alternate jDr opposite. When they occur 

 on the stump or on roots they are not arranged in any regu- 

 lar order. There are two kinds of buds flower-buds, 

 which develop into flowers and fruit; and leaf -buds, which 

 develop into leaves and branches. These can generally be 

 distinguished from each other by their shape and size and 

 by cutting through them and noting their construction. 

 Flower-buds are generally more liable to injury from 

 climatic changes than leaf-buds. 



The Leaves of our trees vary much in size and shape. 

 They are simple when composed of but one piece, as the 

 leaves of the Oak, Maple, and Birch, and compound when 

 composed of more than one piece, as the leaves of the 

 Locust, Ash, and Black Walnut. Leaves are made up of a 

 framework filled in with cellular tissue and covered with 

 a thin skin. This skin has very many small pores in it 

 called stomata, through which the plant takes in carbon 

 dioxide from the air and gives off oxygen and water. 



All our trees shed at least a part of their leaves each 

 year. All the broad-leaved trees and the Tamarack shed 

 their entire foliage yearly, while our so-called evergreen 

 trees lose a part of their leaves each year. The length of 

 time leaves remain on this latter class of trees varies from 

 two or three years, in the case of W 7 hite Pine growing in 

 very severe locations, to perhaps eight years, in the case 

 of Red Cedar favorably located. The time that leaves 

 remain on the branches of evergreens depends to some 

 extent on the location and age of the individual tree. 



The following table gives the approximate length of time 

 that leaves of conifers remain on trees in Minnesota: 



