June, 1915.] 



Ray Pits of Conifers. 



547 



were not, as a rule, filled to this extent; but, in general, it may be 

 stated that the rays of Larix are, during winter, stored with starch 

 through fifteen years of growth. 



Such reserves have been found to be used for two main pur- 

 poses, the production of leaves and of seed. In rare instances, a 



Fig. 5. Fig. 6. 



Fig. 5. Curve showing variation in size of ray pits of Picea sitchensis, 

 through one annual ring of 83 tracheids, plotted on same scale as Larix, 

 except that the horizontal scale of Larix is four times as great because of 

 the fewer number of tracheids. 



Fig. 6. Curve showing variation in size of ray pits of Picea canadensis, 

 through one annual ring of 31 tracheids, on same scale as Fig. 5. 



portion may be diverted to the growth of wood, but this is not 

 usual. Use of the reserves for seed production will occur, as a 

 rule, at periods of from two to several years; hence annual rigns 

 will occur not subject to any modifications from this source. On 

 the other hand, that used for the regeneration of leaves wnll be 

 used yearly, and every annual ring will be subject to structural 

 modifications by this factor. 



