Supposed Hybrid of the Black and Shingle Oaks 325 



VELUTINA 



Transverse (plate XIII, fig. 2; plate XIV, figs. 2, 5). The 

 pith cells are somewhat more variable in size than in imbricaria, 

 and their arrangement gives a more compact structure, with smaller 

 intercellular spaces. The narrow pith rays are much more 

 numerous, and stand out sharply against the wood masses as 

 crooked, irregular, uneven lines. The ray cells are a little 

 broader and somewhat longer, and more irregular. Protoplasmic 

 connections occur as in imbricaria. Wood parenchyma is more 

 abundant throughout both spring and summer wood, and in the 

 latter is scattered in numerous wavy short tangential chains. 

 Wood fibers are more abundant in the spring wood, especially 

 near the broad rays. In the summer wood they are grouped in 

 smaller masses, giving that part of the growth ring a much less 

 compact and solid appearance. The radial arrangement of the 

 fibers discernable in imbricaria is more or less broken up by masses 

 of wood parenchyma, and the growth rings are not so sharply 

 defined. Angular tracheids are plentiful in the spring wood, and 

 roundish ones are scattered sparingly through the summer wood. 

 The vessels of the spring wood are not so abundant or so large 

 as in imbricaria, and do not extend so uniformly or so completely 

 across the spaces between the broad medullary rays, but have 

 a tendency to be bunched together into irregular groups. The 

 few summer vessels are somewhat smaller than those of imhricaria . 

 Compound vessels, or two vessels closeh' adjoining, are seldom 

 found in velutina. The protoxylem is not massed into a few well- 

 defined areas, as in imbricaria, but is scattered, appearing as 

 numerous small groups of a few cells each. The sclerenchyma of 

 the bast, which appears as a band in young twigs and which in 

 imbricaria was merely sinuate, is here deeply scalloped. 



Tangential (plate XIII, fig. 9 ; plate XIV, fig. 8) . The broad 

 pith rays of the younger stems present a more broken aspect 

 than in imbricaria, being traversed with sheets of woody fibers 

 instead of strands. Accordingly the stringy appearance noted 

 in that species is quite wanting here. The uniseriate rays are 

 more numerous than in imbricaria, and they average consider- 

 ably shorter — from five to nine cells. They are not so straight 

 or so uniformly parallel, and their distribution is not so regular. 

 Occasionally they are two cells in width in the middle of a ray. 



