ASPEX REPRODUCTION AND MANAGEMENT 391 



way. A microscopic examination of their contents showed that the 

 great mass of capsules were sterile, containing nothing but pappus. .\ 

 few capsules, however, which were invariably distinguished in external 

 appearance by having a crooked top or beak instead of a straight, sharp 

 point, were found to contain a single seed which appeared to be nor- 

 mal. As these seed-bearing capsules occurred on an average only once 

 in every 500 capsules examined, the amount of seed produced is in- 

 finitesimal. 



The development of the fruits was watched continuously on excised 

 branches placed in water in the laboratory of the Experiment Station, 

 as well as by several visits to the trees. Both on the trees and excised 

 branches when the capsules approached maturity the entire spikes of 

 fruit dried up and frequently fell before the capsules opened. In other 

 cases some of the larger capsules opened, but apparently prematurely, 

 as they became dry and hard and infrequently split open sufficiently to 

 free the contents of "cotton." Not over a dozen beaked seed-bearing 

 capsules of normal development and dehiscence were discoevered upon 

 all of the trees. 



Under these circumstances it would hardly be expected that repro- 

 duction by seed would be abundant, since pistillate trees occupy only a 

 very small portion of the aspen type ; only about 0.2 per cent of the 

 capsules on these trees start to set seed and only 5 per cent at most of 

 these succeed in producing and dispersing normal seed. Probably in 

 many years there is even less production than this, and possibly in 

 some there may be greater, although this spring was favorable, l3eing 

 unusually wet and without frost. 



Staniinate Flowers 



The staminate flowers are more abundant than the pistillate, oc- 

 curring in scattered patches within well defined limits at all elevations 

 in the aspen belt. A typical example of this occurs on the Kxperiment 

 Station grounds, where there are two stands, one an old 100 to 1 10- 

 year-old stand, with a ])artly suppressed understory of about 25-year-old 

 trees coming into the openings below, and an cvcn-aged 40 to 50-ycar- 

 old .stand, with clearly defined limits. Presumably the latter originated 

 after a fire which ran over a portion of the older stand. Nevertheless 

 the old stand and the understory blossom profu.sely every year with 

 staminate flowers, while the younger stand has been entirely sterile for 

 the last six years at least. Many other stmds are known which can 

 be coimted upon to bear staminate flowers every year, while adjacent 



