50 KANSAS UNIVERSITY SCIENCE BULLETIN. 



by means of the bleached leaves. These were from various 

 parts of the United States, and had been given various classi- 

 fications: Q. acuminata (Tennessee), Q. acuminata (North 

 Carolina), Q. acuminata (Lake Champlain), Q. prinus L. 

 (Douglas, Kan.), Q. prinus L. (Florida), Q. prinus discolor 

 (Illinois), Q. castenea Willd. (place of collecting not given). 



A microscopic examination showed that those classified as 

 Q. acuminata were identical with No. 1 of the four studied. Of 

 the others, Q. prinus from Douglas, Kan., Q. prinus discolor 

 from Illinois, and Q. castena, were identical with No. 3. Q. 

 prinus L. from northern Florida was like No. 4 in every par- 

 ticular, with the exception of epidermal hairs, which were en- 

 tirely lacking. In respect to the large lower epidermal cells 

 with wavy walls, which was the most distinguishing character- 

 istic of No. 4, it was identical. None was found like No. 2. 



As a further check on this method of classification, sections 

 of leaves from nine different specimens of Q. prinoides found 

 in the herbarium were taken and bleached as before. This oak 

 was selected because of its resemblance to those studied. One 

 of the specimens was from Douglas, Kan., one from Illinois, 

 and the other seven were collected near Troy, Kan., in Sep- 

 tember, 1913. By the methods used in the study of the four 

 oak under investigation it was found that prinoides has 1023 

 stomata per sq. mm. The epidermal hairs are like those of 

 No. 2, except that they were uniformly much shorter. The pali- 

 sade cells were closely compacted, as in No. 2, and the cells of 

 the epidermis similar to those of No. 2. The smaller branches 

 of the veins were much more prominent than those of any of 

 the four oaks being studied. These characteristics held good 

 for every specimen of the nine taken, they being so exactly alike 

 that there was no variation that would distinguish one from 

 the others. 



This seemed enough evidence to conclude that the wide and 

 constant differences found in the four oaks under consideration 

 were constitutional and not modificational variations. 



PETIOLE AND MIDRIB. 



Figures 34 to 37 show cross sections of the petioles of the 

 leaves at the base of the leaf blade. They show some differ- 

 ences in the shapes of the petioles and of the various tissues, 

 more especially in the shape of the middle bundle. In Nos. 3 

 and 4 the bast, phloem, and xylem regions make continuous 



