240 Minnesota Plant Life. 



rather dense drooping catkins. The pistillate flowers, produced 

 on other trees, are green in color, and likewise gathered in 

 pendent clusters. The capsule opens by three clefts and is 

 regarded as composed of three carpels. A considerable num- 

 ber of silky-tufted seeds are produced in each capsule. 



The other poplars need no special mention since they are 

 not indigenous to the state. One of them, the Lombardy pop- 

 lar, with its spire-like habit of growth, is an attractive and val- 

 uable ornamental tree. It is propagated by cuttings and seems 

 to have lost the power of fruiting. No doubt almost all the 



I: 



FIG. 109. Clusters of willow flowers; on the left the pistillate flowers and on the right the 

 staminate. Each pistillate flower consists principally of a single fruit-rudiment, and each 

 stamiiiate flower of two, or sometimes a larger number of stamens. After Atkinson. 



Lombardy poplar trees in America might be traced back to a 

 single poplar egg. The tree which developed from the em- 

 bryo plantlet was originally propagated by cutting the twigs 

 and planting them in the soil. The process was repeated and 

 in this way a vast number of Lombardy poplars have come to 

 exist a very odd thing, indeed, when one thinks of it and com- 

 pares it with the behavior of animal eggs. 



Willows. The willows of Minnesota are not all trees like the 

 poplars. The majority are shrubs some of them low bushes 

 like the myrtle-leafed willows in peat-bogs and tamarack 



