MULSOW: DIFFERENTIATION OF OAKS. 277 



ACORNS. 



The size and structure of the acorns is noticeably different 

 in all of these oaks ; yet there is a somewhat close resemblance 

 between the acorns of Q. rubra and Q. schneckii. The cup in 

 Q. schneckii is deeper and has coarser bracts; the acorn is 

 not so large, and is more pointed. The acorn of Q. macrocarpa 

 is much larger than the others, and the acorn of Q. coccinea 

 is much smaller. The shell of the acorn of Q. rubra is thicker 

 than the others. The inner surface is covered with hair-like 

 outgrowth in all except in Q. macrocarpa, which, however, 

 has a thin layer of cells forming a lining membrane. The 

 shell wall of Q. coccinea is much thinner than the others. 

 (Figs. 55 to 58, inclusive.) 



The starch grains were larger in Q. rubra and Q. schneckii, 

 being about .0076 mm. in diameter, and in the others about 

 .0062 mm. The acorns are more numerous on the branches of 

 Q. coccinea and Q. rubra. For relative sizes and shapes see 

 figs. 51 to 54. 



CONCLUSIONS. 



From this study of the oak it appears that there are enough 

 differences in the various tissues of the oaks to enable one to 

 distinguish the species by histological methods. There were 

 found differences in the leaf sufficient to distinguish the dif- 

 ferent species, and in addition to this there are differences in 

 the stem and acorns which would enable one to further dis- 

 tinguish the species. 



Botanical Laboratory. 

 University of Kansas. 



