THE WOODS IN THEIR SUMMER FOLIAGE 235 



46. The Fruit of Trees, Shrubs, and Vines. 



MATERIAL : Fruit and fruit-bearing twigs of all species to be studied ; 

 twigs with small fruit to be added to the school herbarium ; large seeds 

 to be kept in boxes. Dissemination of seeds is important. From the 

 larger seeds remove the coverings and try to find the germ-leaves, the 

 first leaflets, and the radicle, or rootlet. Plant the seeds and observe 

 the young trees. 



1. We observed last spring that the little pods on the 

 fertile catkins of willows, of the quaking asp, and of the 

 cottonwood soon opened and shed a large amount of fine 

 white cotton. Closer inspection showed a tiny seed attached 

 to each tuft of cotton, and by means' of these tufts the seeds 

 often sail many miles and are dropped everywhere. If they 

 happen to fall on bare, moist ground, they will grow at once. 

 Later, in July and August, I observed thousands of young 

 willows, asps, and cottonwoods growing on the moist sand 

 banks near lakes and rivers. Where a tract of forest has 

 been burned, a poplar thicket will almost invariably succeed 

 the burned trees. Later other trees slowly return, and in 

 course of time kill out the poplars or take the place of those 

 which die of old age, as the poplars are short-lived ; but it 

 probably takes from thirty to fifty years before this change 

 is well under way. Why do such small and light seeds as 

 those of willows and poplars have a better chance of finding 

 a suitable place early in spring than later in the season ? 

 How are bare sand banks and mud flats near rivers made ? 



2. The seeds of elms and birches are little nutlets pro- 

 vided with a winged margin, by means of which they are 

 carried considerable distances from the trees. When were 

 the elm seeds ripe ? When were the birch seeds shaken out 

 of the catkins ? The seeds of ashes and maples are also 

 provided with wings, and if you drop some from a second or 

 third story window, you can observe how they sail. As these 

 trees grow oten near streams, their seeds frequently drop 



