390 JOURNAI^ OF FORESTRY 



favorable conditions, it has been shown that the reproduction must be 

 attributed to root suckers to a much greater extent than has been cus- 

 tomary. - 



Early in the work of the Experiment Station upon aspen it was rec- 

 ognized that aspen seedlings were very rare indeed, and during the six 

 years covered by this study several hundred young aspen trees have 

 been uprooted wherever they have been found in recent burns, isolated 

 situations, and whenever any peculiarity in appearance might indicate 

 that the tree was possibly a seedling. However, not a single seedling 

 has ever been found. It is also usually possible to tell whether sap- 

 lings up to about three inches d. b. h. are sprouts by shaking them 

 first in one direction and then in another. It will be found that they 

 move very easily in one direction, but are stiff in a direction at right 

 angles to this, on account of the single, straight, shallow, horizontal 

 root from which the tree came as a sucker. The motion which tends 

 to twist this root is much easier than the one at right angles to it. 

 Saplings showing this peculiarity are clearly sprouts. Many saplings 

 which do not show this have been investigated and have been invariably 

 found to be sprouts which have arisen from such large roots or so near 

 stumps that they are relatively immovable in any dii^ection. 



REPRODUCTION BY SEED 



Pistillate Flowers 



A study of aspen seed was made to discover, if possible, the reason 

 for a lack of seedHngs. In 191 3, 1914, and 191 5 no seed at all could be 

 found ; in fact, no pistillate catkins were seen, although staminate 

 flowers were found abundantly in scattered localized areas. In 1916 a 

 little "cotton" was found blowing from some unknown source, but 

 careful examination revealed the fact that there was no seed attached 

 to the pappus. In the spring of 1917 it happened that a number of 

 trees were found fruiting. These trees formed a fringe along the lower 

 edge of the aspen belt where it adjoins the mixed oak and sagebrush. 

 Only these marginal trees for a distance of about a hundred yards were 

 fruiting, nearly every tree being free of side shade on one side. The 

 trees in the interior of the stand bore staminate catkins, as they had 

 done the two years previously, and those adjoining on the ends of the 

 fruiting strip were either sterile or staminate. At the time of discovery 

 the seed capsules were about half grown and appeared normal in every 



^ Weigle. W. G., and Frothingham, E. H. "The Aspens : Their Growth and 

 Management." U. S. Forest Service Bull. 93: 19, 1911. 



