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48 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN [VOL. 10 



pores. However, it is felt that this particular specimen is abnormal or juvenile 

 as there is a fairly wide conspicuous band, 1—3 mm wide, near the center of the 

 stem which is composed of great numbers of closely placed pores and abundant 

 paratracheal parenchyma. This concentric band resembles the early wood of 

 ring-porous species. It is possible, therefore, that were it not for the effect of 

 this seemingly abnormal or juvenile condition on the remainder of the xylem 

 cylinder, the concentric growth marks elsewhere in the stem of Diomma would 

 be of regular occurrence as in Sohnreyia. Both genera exhibit diffuse-porous 

 wood. 



Imperforate tracheary elements in both genera are fiber-traeheids bearing 

 pits with rounded borders and extended inner apertures. Length varies from 

 very short to short (table 1; Chattaway 1932). In Diomma and Sohnreyia 

 pores (fig. 5A, C) are mostly distributed as radial multiples (2-10 cells), over 

 half appearing in this form. It is interesting to note the occurrence of occa- 

 sional chains of pores in each genus (table 2). Pores ace circular in outline and 

 extremely small to moderate-sized in diameter (table 1; Chattaway 1932). 

 Vessel elements are short to very long, and end walls are oblique, but generally 

 not less than 45° (table 1; Chattaway 1932). Intervascular pitting is strictly 

 alternate, although in Diomma there is a local tendency to opposite pitting. 

 Perforation plates are simple, but in Diomma vestigial bars in the form of 

 mucros were occasionally observed projecting from the rim of the plate. 



Vascular rays are generally heterocellular in Sohnreyia (fig. 5D) the multi- 

 seriate rays exhibiting upper and lower uniseriate " wings" varying from a 

 single marginal cell to 7 cells high. Vascular rays in Diomma (fig. 5B) are essen- 

 tially homocellular and consist mostly of procumbent cells. The sporadic occur- 

 rence of multiseriate rays with terminal uniseriate ''wings" was noted,- but 

 cells in these wings were generally procumbent. Occasionally a small * 'square" 

 cell was observed in the radial view. Uniseriate "wings" are mostly less than 

 6 cells in height. 



Vascular rays in Sohnreyia are regularly triseriate, with some biseriate rays. 

 The uniseriate and quadriseriate conditions are rare. In Diomma the biseriate 

 ray is most abundant with uniseriate rays of fairly common occurrence. Tri- 

 seriate r&ys are very scarce. 



Axial xylem parenchyma in both genera occurs apo- and paratracheally. In 

 Sohnreyia (fig. 5C) concentric bands 2-3 (4) cells wide are of regular occur- 

 rence. A few strands of parenchyma were also noted in association with vessels 

 or groups of vessels. Concentric bands of axial parenchyma also appear in 

 Diomma (fig. 5A), but these are mostly 1 cell wide and are irregularly distrib- 

 uted on the transverse section. Incomplete sheaths of axial parenchyma, 1-2 

 cells wide, are associated with the vessels. 



It is apparent from the above description that the xylem anatomy of Sohn- 

 reyia and Diomma is very similar. A few points of difference are however noted 

 in the following features: (1) concentric bands of axial parenchyma are 2-3 

 cells wide in Sohnreyia and only 1 cell wide in Diomma, (2) vascular rays are 

 usually heterocellular in Sohnreyia and essentially homocellular in Diomma, and 

 (3) vascular rays are regularly triseriate in Sohnreyia and biseriate in Diomma. 

 Tn considering the significance of these differences thought should be given to 

 the fact that only one wood specimen of each genus was available for analysis, 



