6 



Certain injuries decrease while others increase seed quality. A com- 

 parison of healthy and unhealthy trees shows the following germina- 

 'tion per cents: Healthy yellow pine, 64; unhealthy yellow pine, 71; 

 healthy blackjack, 78; unlieal thy blackjack, 61. In classifying the 

 trees with respect to health, those affected by heart rot, insects, 

 mistletoe, dying top, fire scars, and suppression are classed as "un- 

 healthy," while those showing no indications of disease or injury are 

 classed as "healthy." These terms mean but little, however, unless 

 we inquire into the actual condition of the tree. Grouping the 34 

 trees classed as unhealthy according to the nature of the injury, the 

 following interesting comparison is derived: 



TABLE 2. Comparative quality of seed from healthy and unhealthy trees. 



Yellow pine affected by heart rot shows a germination 3 per cent 

 higher than that of sound, healthy yellow pine. This difference, based 

 upon only 10 trees, is hardly sufficient to establish the conclusion 

 that heart rot increases germinative quality, but at the same time 

 tends to show that at least the seed of such trees is not inferior to 

 that of sound trees. The smallness of the effect is probably due to 

 the fact that the rot works upon the heartwood exclusively and 

 does not directly attack the vegetative life of the tree. If the rot 

 should become sufficiently advanced to reduce materially the vitality 

 of the tree, it is probable that the quality of the seed would be im- 

 paired and the quantity diminished. On the other hand, the fungus 

 in its earlier stages may act as a stimulus, as in the case of "spike 

 top" and fire scars, considered in the paragraphs following. 



Spike tops show a germination 15 per cent higher than that of the 

 Jiealthy yellow pine. "Spike top " is the common term applied to trees 

 with dead leaders, generally caused by some mechanical injury, most 

 frequently lightning. The wound is usually followed by a fungous 

 attack. The leader dies back from year to year, and as the upper 

 branches drop away a straight shaft is left projecting above the 

 living portion of the crown. The injuries causing spike top evi- 

 dently act as a stimulus upon seed production. This peculiarity 

 apparently nature's provision for the perpetuation of the species 

 although not fully understood, is a matter of common observation. 



[Cir. 196] 



