Supposed Hybrid of the Black and Shingle Oaks 321 



ference in the time of maturity of the two kinds of flowers of 

 velutina and imbricaria may be very significant. The first 

 ripened pistils of imbricaria are ready for pollination before 

 imbricaria pollen is available, but when there is an abundance 

 of velutina pollen. Thus a favorable condition for hybridization 

 is brought about, and at the same time the direction in which 

 such hybridization will take place is strongly indicated. In 

 other words imbricaria must be XhQ maternal and velutina the 

 paternal parent. Such an assumption is further borne out by 

 the position of the trees in question at Cedar Point, all being 

 near imbricaria trees, with velutina trees more or less distant. 

 The assumption also is in harmony with Mr. Ward's account of 

 a Leana raised by Mr. W. R. Smith from an acorn of imbricaria. 



Gross Anatomy of the Stem 



The oaks have characteristically a sharply five angled pith 

 and conspicuous broad medullary rays. The pentagonal pith 

 of the three oaks in question is decidedly asymmetrical, being con- 

 siderably longer than broad. In velutina it is in general much 

 larger than in the other two, and averages nearly twice as long 

 as broad. The smaller pith of imbricaria has much the same 

 shape, being both shorter and narrower. Leana has a greatly 

 elongated and much compressed pith, thus presenting in one 

 dimension the condition of velutina, and in the other that of 

 imbricaria (plate XIV, figs. 1-3). 



In small branches of imbricaria, 1 cm. in diameter, the broad 

 rays are conspicuously arranged in pairs producing with the 

 enclosed wood masses the appearance of five distinct radiating 

 bands. Certain other oaks also possess this feature, noticeably 

 the English oak (Q. robur), where the radiating bands are more 

 narrow but equally conspicuous. Velutina, on the other hand, 

 shows numerous large medullary rays in addition to the five 

 pairs at the angles of the pith, and the bands, so striking in im- 

 bricaria, are hardly conspicuous here. Rubra and coccinea present 

 much the same condition as velutina in this respect, although 

 in rubra the rays are somewhat less distinct, and the bands even 

 less evident, while in coccinea the more numerous rays are rather 

 regularly distributed and the bands disappear altogether. Leana 



