16 THE LIFE HISTORY OF A TREE 



containing stamens only ; the females are small, bud-like, and 

 inconspicuous till fertilization takes place, when they grow 

 into nuts. Species which have separate male and female 

 flowers on the same tree are called monoecious species. In 

 willows, poplars, and juniper, the male and female flowers are 

 on different trees, some trees having male flowers only and 

 others having females only; these species are said to be 

 dioecious. 



The seeds of many trees are aided in their dispersal by 

 means of wings (e. g. Scotch pine and other conifers), or by 

 hairs (e. g. poplars and willows). In sycamore, Norway maple, 

 ash, elm. and birch, the fruit is winged. Seeds aided in this 

 way are able to travel further than those with no such pro- 

 vision, with the result that we find young plants of such 

 species coming up at a great distance from the mother tree, 

 whereas young oaks or other plants whose seeds are heavy 

 will not be found naturally reproduced at any distance from 

 the mature tree, unless carried and dropped by squirrels or 

 birds. The seeds of alder and willows are often conveyed by 

 running water. 



Besides reproduction by seeds, most of the broad-leaved 

 trees are able to spring up again by means of stool shoots 

 after the tree has been cut down, or by suckers from the roots. 

 This power varies in the different species, and on it depends 

 the production of coppice woods. Some conifers, especially 

 Sequoia sempervirens, have the power of sending up coppice 

 shoots, but the power is so weak with most conifers that it 

 may be neglected for all practical purposes. 



The terms ' broad-leaved tree ' and ' conifer ' or ' coniferous 

 tree ' will often be used to distinguish between two classes of 

 our forest trees. For our purposes a broad-leaved tree may 

 be defined as a species whose leaves are more or less broad 

 and flat, and whose foliage is usually deciduous, the leaves 

 falling off in autumn, leaving the tree leafless in winter. 

 Quercus Ilex affords a good example of an evergreen broad- 



