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



Secretory cells retain the ergastic substance (e.g. oil, mucilage, resin), Avhereas 

 cells in a secretory epithelium release ergastic material, by one means or another, 

 into the intercellular space. A secretory intercellular space which is pocket-like 

 and of more or less definite shape and size is termed a secretory cavity (Stern 

 1954). Secretory cavities occur in the pistils and leaves of Dion} ma and Sohn- 

 reyia. 



Secretory cavities in the pistils of Diomma (fig. 1A-C) and Sohnreyki are 

 essentially similar in form, number and location. Two cavities are present in 

 each pistil, one in the median dorsum of each carpel, close to the outer wall. 

 The secretory cavities are elongate, tapering gradually from the more or less bul- 

 bous base toward the attenuate 1 apex. A yellowish material was observed in these 

 pouches in one specimen. 



The leaves of Sohnreyia and all species of Diomma are characterized by the 

 presence of secretory cavities in the mesophyll. These cavities vary from 72 to 

 172 fx in diameter and average about 100 fx. The secretory epithelium appears 

 to be 1 or sometimes 2 cell layers thick. Cavities nestle within a basket-like net- 

 work of vascular bundles (figs. 3A, 4). 



In addition to secretory cavities, leaves of all species of Diomma possess 

 elongate secretory cells distributed among the chlorenchymatous cells of the 

 palisade mesophyll (fig. 4). These are larger in paradermal section than the 

 palisade cells and average 26 fx in diameter, ranging from 14 to 47 /m. In Length 

 they approxin ate that of the palisade cells. 



The distribution of secretory structures in the available specimens of the 

 two genera is summarized in the key below. It should be emphasized that the 

 positions given are apparently not immutable, but may vary to a certain degree. 

 For example, in species described as having secretory cavities located along the 

 margin of the leaflet, an occasional cavity may occur elsewhere in the leaflet. 

 1. Secretory cells present in leaves and scattered among the chlorenchymatous 

 cells of the palisade layer. Diomma. 

 2. Secretory cavities confined to the margin of the leaflet. "Diomma ulei 

 distribution" : 



E. lie 8646; J. A. Steyermark 75699, 58982, 59798; J. A. Steyer- 

 mark & J. J. Wurdack 938, 1099; B. Maguire, J. J. Wurdack & 

 C. Maguire 42315, 42329. 

 2. Secretory cavities dispersed throughout the mesophyll of the leaflet. 

 "Diomma fruticosa distribution": 



J. A. Steyermark 60820; B. Maguire J. J. Wurdack 33808. 

 1. Secretory cells absent in leaves. Sohnreyia. 



. XYLEM ANATOMY 



Whether the concentric marks that appear on the transverse sections of both 

 Diomma and Sohnreyia (fig. 5C) are related to seasonal increments in s|^m 

 diameter is unknown. It is probably best therefore, to refer fo these lines in a 

 general way as concentric growth marks (Chowdhury 1939). Concentric growth 

 marks in Sohnreyia are regularly spaced and obvious because of a pronounced 

 thickening in the walls of the imperforate tracheary elements and the presence 

 of a band of axial parenchyma associated with these thicker-Availed fibers. 

 Growth marks in Diomma are irregularly spaced and seem to be erratically pro- 

 duced. Some of these rings are visible because of their delimitation by a narrow 

 band of axial parenchyma (fig. 5A) and/or close tangential aggregations of 



