MISTLETOE INJURY TO CONIFERS. 31 



the same trees. Given the general average percentages of germina- 

 tion of 30 for the former and 40 for the latter, it seems that either 

 from exhaustion of stored materials or tendencies toward abnormal 

 seed production in general the uninfected branch, though suppressed, 

 is still capable of producing a higher quality of seed than the broom. 

 Whether this would be true in the case of young, vigorous brooms 

 is doubtful. Seeds from the uninfected . branches of the same 

 strongly suppressed trees used in the above experiment gave a gen- 

 eral average of 15 per cent below that of seeds taken from vigorous 

 uninfected trees of the same age, species, and habitat. The per- 

 centage of 65 for the uninfected and 40 for the infected shows quite 

 clearly that suppression by mistletoe causes a serious falling off in 

 the quality of the seed of its host. 



The experiment was conducted in the following manner. Col- 

 lections of cones were made from each of five strongly suppressed 

 and five uninfected trees of all three species. This included one col- 

 lection from the brooms, one from the uninfected branches of each 

 of the suppressed, and one collection from each of the uninfected 

 trees; in all, 45 different collections. One hundred seeds were ex- 

 tracted from each collection and germinated in sand at an average 

 temperature of 35 C. Counts were made at different intervals dur- 

 ing the progress of the test, which was continued for 90 days. Con- 

 siderable difficulty was experienced in procuring the required num- 

 ber of seeds for all conditions, owing to the sterility of the cones 

 on the old brooms. With the increasing age of the broom the seed 

 production falls off, until, as it is with most species, no cones are 

 produced at all. Seeds from recently formed brooms were not tested. 

 It is supposed that they would show a higher percentage of germi- 

 nation. The cones on badly suppressed trees are very often aborted, 

 with shriveled, undeveloped sporophylls, and are frequently infested 

 by cone beetles and cone worms. Seeds, if produced in such cones, 

 are usually below the normal size. A study of microtome sections 

 of the staminate flowers from heavily infected lodgepole pine showed 

 that there was a reduction in the number of pollen mother cells. The 

 staminate flowers when compared with those of normal trees of the 

 same age and condition were found to be uniformly smaller. The 

 sporophylls on the more fertile or convex side of the young pistil- 

 late cones very frequently bore only one ovule (megasporangium), 

 a condition not observed in cones from healthy trees. 



HOST AFFINITIES IN RELATION TO SILVICULTURE. 



For practical purposes the following statements on the host re- 

 quirements of the mistletoes of coniferous trees will be found to 

 be of some interest with regard to the silvicultural management of 

 forests. 



