52 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN ' [VOL. 10 



are scarce. The condition is also known in certain aborescent species of Lobelia 

 (Krause 1921) and in many shrubby genera of Strobilanthinae-Acanthaceae 

 (Bremekamp 1944). 



According to the results of an extensive survey of nodal conditions and leaf 

 anatomy currently under way in the laboratory of Dr. Richard A. Howard, 

 petioles of Rutaceae are characterized by a ring of vascular tissue without asso- 

 ciated medullary bundles. This condition has been reported above for Diomma. 

 Petiolar anatomy in Simaroubaceae also consists of a ring of vascular tissue, but 

 with or without associated medullary bundles. 



Plants with the palm-like appearance attributed to Diomma are referred to 

 in German botanical literature as Schopfbaume or tufted trees. The occurrence 

 of this manner of growth among dicotyledons appears to have significance only 

 at the species, or at most the genus level, for it is widespread among the species 

 of many families: e.g. Theophrastaceae (Clavija, Theophrasta) , Compositae 

 (Verononia spp.), Caricaceae (Carica), Meliaceae, Simaroubaceae, Sapindaceae, 

 and Anacardiaceae (Harms 1912, 1940; Mildbraed 1922). It should not seem 

 strange, therefore, to place the schopfbaumartig Diomma in Rutaceae, for we 

 already know that Sohnreyia and Spathelia are of this form (Krause 1914; 

 Marie-Victorin 1948), as well as the following Rutaceae: Leptothyrsa (Engler 

 1931), certain species of Cusparia (Engler 1931), and Dictyoloma peruvianum 

 (Maebride 1949). 



In order to locate the most natural position for Diomma among the infra- 

 familial taxa of Rutaceae, it has been necessary to review more or less closely 

 the characteristics upon which these taxa have been based. Moreover, when the 

 authors reached a tentative hypothesis in this regard, careful examination of 

 the possible near relatives of Diomma was indicated. Sohnreyia; which will be 

 demonstrated as probably the closest ally, has been analyzed in detail and the 

 results are reported above. Spathelia, a somewhat more distant relative, was 

 studied in less detail. The actual results of the observations on Spathelia will be 

 incorporated in the following sections. 



Comparison of Diomma with Sohnreyia. 



Diomma and Sohnreyia are similar to each other in the following respects: 



(1) both exhibit a schopfbaumartig appearance, (2) both are presumably mono- 

 carpous, secretory cavities are present in leaves of each, (4) the basic struc- 

 ture of the flower and fruit is the same in each genus, (5) both possess apo- 

 tropous ovules, (6) pistils in each genus contain 2 similarly placed secretory 

 cavities, (7) each genus is polygamous, (8) xylem anatomy is very similar in 

 these genera, (9) pollen grains are apparently alike, and (10) pinnately com- 

 pound, estipulate leaves occur in each genus. Despite these many resemblances, 

 Diomma and Sohnreyia are distinct and differ in the following characters: (1) 

 secretory cells are present in leaves of Diomma but are lacking in Sohnreyia, 



(2) appendages of staminal filaments in Diomma (except D. ulei\ appear to be 

 lateral wing-like proliferations of the filaments, whereas in Sohnreyia, staminal 

 processes are fused with the ventra of the filaments for most of their length, but 

 the ligulate apex is directed ovary-ward, (3) ovaries in female flow r ers of Diom- 

 ma are almost sessile (gynophore rudimentary) but in Sohnreyia ovaries are 

 conspicuously stipitate (fig. IF), (4) insides of the locules of the ovary and 

 fruit are entirely glabrous in Diomma but pubescent in Sohnreyia, (5) the stel- 

 late hairs characteristic of Diomma have not been observed in Sohnreyia. 



