A, comparison of yellow pine and blackjack shows an average yield 

 of 1.8 bushels of cones per tree for the former and 1 bushel for the latter. 

 This difference is attributable mainly to a difference in the size of 

 the trees, the yellow pines on account of their greater age being on 

 the average much larger than the blackjacks. A comparison of the 

 classes with respect to the amount of seed produced by a pound of 

 dry cones gives 1.3 ounces for the yellow pine against 1.7 ounces for 

 the blackjack. It therefore appears that, although the younger 

 trees yield less cones, when the amount of seed produced by a given 

 quantity of cones and the vitality of the seed are considered, these 

 trees are better seed producers for their size than the older trees. 

 In comparing the two age groups from 140 to 250 years and from 

 260 to 400 years we find, as in the case of the blackjack and yellow 

 pine, a considerably greater yield of cones for the older trees. The 

 amount of seed produced by a pound of cones is, however, the same 

 for both groups. The difference of cone production is much less 

 pronounced between these two age groups than between the black- 

 jack and yellow pine, because many of the trees included in the 

 lower-age class have passed beyond the blackjack stage. Practically 

 no data are available on trees below 140 years, since the trees were not 

 felled, and only a small number of cones were picked from each tree. 



A comparison of the healthy and unhealthy yellow pine shows only 

 a slight difference in cone production. There appears a pronounced 

 difference between the healthy and unhealthy blackjack, but, since 

 we have accurate data for only two unhealthy blackjacks, this com- 

 parison is not conclusive. Furthermore, as in the case of germination ; 

 a comparison of healthy and unhealthy trees is of little significance 

 unless we consider the nature of the injury in the unhealthy trees. 



A comparison of the trees classed as unhealthy, considering the 

 nature of the disease or injury, is shown in Table 3. 



TABLE 3. Comparative yield of cones from healthy and unhealthy trees. 



Although the yellow pines affected by heart rot show a yield of 

 0.3 bushel more than the healthy trees of this class, the difference is 

 probably due mainly to the fact that the trees affected by heart rot 



[Clr. 196] 



