SPECIES FOR STREET-PLANTING 31 



As a result the nursery-trained oaks grow as fast as the 

 hard maples. 



Pin Oak {Quercus palustris Linn.) . — Planted more exten- 

 sively than others of the genus is the pin oak. Its charac- 

 teristic pyramidal form distinguishes it from most decidu- 

 ous trees. The stem rises like an unbroken shaft. The 

 branches are slender and stretch out almost horizontally, 

 those at the bottom being the longest. Its deeply cut, light 

 green, shining leaves give the foliage a massing that is fern- 

 like in grace. The lower branches have a tendency to 

 droop; but this habit can be corrected by proper pruning. 

 The dense branching of this tree causes some of the twigs 

 to die, and it is these spurlike projections from the branches 

 that form the "pins" which give the tree its common name. 



The oaks have two sets of flowers — staminate, or male 

 and pistillate, or female. The two sets of flowers are borne 

 on the same tree, and hence the flowers are said to be mo- 

 noecious — of one household. 



Some oaks, such as the white oak, mature their acorns 

 the same season in which they flower; but the pin oak 

 belongs to the group of biennials — the oaks that take two 

 years for the fruit to mature. In autumn, after the spring 

 flowering, the acorns of these trees are only partly grown ; 

 they remain in that condition during the winter, continue 

 their growth the next summer, and mature in the fall of the 

 following year. 



The leaves of the pin oak turn a deep scarlet in autumn, 

 and as in the case of most of the oaks, they fall late in the 

 season. They are not like the leaves of the. white oak, 

 however, some of which remain on the trees all winter. 



Red Oak {Quercus rubra Linn.).— There is a street in 

 the city of Washington which once seen cannot be forgot- 



