276 KANSAS UNIVERSITY SCIENCE BULLETIN. 



in the first year's growth to break up the epidermis, while in 

 the others the epidermis remains unbroken for at least five 

 years, and usually much longer. The number of water tubes 

 per unit area is much less in Q. macrocarpa than in the others. 

 There is the largest number of water tubes in Q. schneckii. 

 It also has a smaller proportion of pith and parenchyma of the 

 cortex than the others. The bast and phloem in Q. schneckii 

 and macrocarpa are almost entire, while in the others the bast 

 and phloem are divided. (See figs. 31 to 34.) 



Cross sections of the older stems show that the water tubes 

 in Q. schneckii occupy a much larger space and are more 

 scattered throughout each year of growth than in any of the 

 others. In Q. rubra, and especially Q. coccinea, the water tubes 

 are usually found in the first part of each year's growth, and 

 much less scattered through the whole year's growth than in 

 Q. schneckii. In Q. macrocarpa there are not so many water 

 tubes and they are not as large or disperse as in the others. 

 (Figs. 43 to 46.) In tangential sections there is a difference 

 in the number of medulary rays per unit area. Thus in Q. 

 macrocarpa, which has the largest number per sq. cm., there 

 are about 108 rays per sq. cm. The rays are also shorter and 

 broader than in the others. In Q. rubra there are 96 rays per 

 sq. cm. A large per cent of these are longer than in Q. 

 macrocarpa, but the per cent of long rays is not as large as 

 in Q. coccinea, which has the least number of rays per sq. cm., 

 there being about 57 per sq. cm. The rays in Q. coccinea are 

 also more slender. In Q. schneckii there are 75 rays per sq. 

 cm., and no very long rays. (Figs. 47 to 50.) 



Macerations of the wood and bast fibers were made by 

 gently heating sections of each in Schultze's macerating fluid, 

 in order to study the comparative lengths of the fibers. The 

 wood fibers of Q. macrocarpa are on an average shorter than 

 the others, all of which are about the same length; however, 

 those of Q. schneckii are slightly broader than the others. The 

 bast fibers are on an average about the same length, except in 

 Q. coccinea, where they are about twice as long as in the others. 

 Thus in Q. coccinea the bast fibers are as long as 1.4 mm.; 

 in the others they average about .6 mm. in length. (Figs. 35 

 to 42.) There was no noticeable difference in size or char- 

 acter of the cells of the wood parenchyma of these four oaks. 



