1960J 



MORPHOLOGY AND RELATIONSHIPS OF DIOM.MA 



53 



Comparison of Diomma with Spathelia. 



The genus Spathelia contains 14 species and is apparently restricted to the 

 West Indies ( Marie- Victorin 1948). It constitutes a monogeneric subfamily of 

 Rutaceae, the Spathelioideae (Engler 1931). This genus has a number of char- 

 acteristics in common with Diomma. 



Plants of Spathelia are characterized, as are those of Diomma, by unbranched 

 trunks with leaves crowded at the apex — Schopfbaume. Monocarpy is a charac- 

 teristic of Spathelia. Leaves are pinnately compound and the leaflets exhibit 

 marginal secretory cavities and scattered secretory cells. Diomma and Spathelia 

 are polygamous genera. 



Floral parts in Spathelia are basically pentamerous as in Diomma. Sepals 

 and petals in Spathelia both possess an apical glandular cavity. A gynophore 

 is present beneath the ovaries in Spathelia; it is always very tiny in female 

 flowers, but may be more or less conspicuous in male flowers. Pollen grains of 

 Spathelia resemble those of Diomma. Both genera produce winged fruits . 



The xylem anatomy of Spathelia vernicosa (Yw; Leon s.n.) is essentially the 

 same as that of Diomma and indeed of many Rutaceae (Heimsch 1942). S. 

 vernicosa exhibits diffuse porous wood. The fiber-tracheids are characterized by 

 minute bordered pits and walls that are from thick to very thick. Pores are 

 distributed mainly as radial multiples some of which contain over 12 pores. 

 Solitary pores are of common occurrence and are more aboundant than pore 

 clusters. Some of the latter are fairly extensive, being 20 or more pores in size. 

 Radial pore multiples verge on pore chain configuration in some instances. The 

 perforation plates are exclusively simple, and vessel element end walls are 

 mostly oblique. Intervascular pitting is strictly alternate and the pits are small 

 with round borders. Vascular rays are heterocellular and 1-3 cells wide. Most 

 rays are uniseriate but biseriate rays are common. Triseriate rays are rare. 

 Although a single wide ( zb 12 cells) band of axial parenchyma occurs in our 

 specimen, it is believed to be of traumatic occurrence, since (1) certain of the 

 cells are irregular and abnormal in appearance, and (2) it is the only band 

 present on the sections. Nevertheless, its presence probably indicates the poten- 

 tial of band formation in the genus. Scanty vasicentric axial parenchyma is 

 regularly present. Only a few strands, or none at all, are in contact with vessels 

 on a given transverse section. 



Many species of Spathelia are characterized by alate staminal appendages 

 more or less similar to those of Diomma (fig. 2F-I). Other species are devoid 

 of these appendages, much as in Diomma ulei. The shape and means of attach- 

 ment to the filament of these appendages differ with the species of Spathelia, 

 the genus being inconstant in this respect. It might be well to recall at this 

 juncture that in species of Diomma exhibiting filament processes, the latter 

 appear as lateral expansions of the filament, and in this Diomma seems to differ 

 from Sohnreyia whose staminal appendages are probably fused with the ventra 

 of the filaments. We note that within Spathelia both the Diomma and the 

 Sohnreyia types of staminal process are present, as well as other types, and even 

 unappendaged filaments. For example, lateral appendages like those in Diomma 

 occur in Spathelia simplex L. (Steam 162 as S. sorbifolia L.) ; scale-like, bilobed 

 appendages occur in S. cubensis P. Wils. (Wright 2192) ; fairly large, almost 

 truncate appendages are found in S. subintegra Marie-Vict. (Wright 2191) ; and 



