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[VOL. 10 



appreciably different from the tubular condition of the corolla in Abolboda 

 and Orectanthe, and the venation reveals no appreciable alterations in this 

 respect. To be sure, Achlyphila is less specialized in its choripetalous condition, 

 but one might assume that presence of staminodia was a primitive character 

 in Abolboda. Certainly the development of style ("ovary") appendages in 

 Abolboda and Orectanthe are advanced characteristics, whatever their signifi- 

 cance may be. Unfortunately comparable data is not available on seed anatomy 

 for the four genera, but I suspect that this will reveal a common basis upon 

 which variations have been evolved. Similar considerations also apply to 

 morphology of the embryo; the three genera for which this is now known all 

 have the same peculiar type, with variations chiefly in size. The most significant 

 anatomical character in Xyridaceae with respect to difficulties in interpreta- 

 tion might seem to be pollen morphology. Much has been made of the difference 

 between Abolboda (with Orectanthe) and Xyris in these respects. Because 

 monosulcate pollen is so basic in the monocots, the nonaperturate condition 

 in Abolboda, Orectanthe, and Achlyphila would seem to. be derived. If this were 

 true, one might also expect a more primitive exine condition in Xyris also. The 

 lack of differentiation of the sexine elements, and their even distribution, appear 

 to be unspecialized. Exine in Achlyphila consists of only one type of sexine 

 element, small pila arranged in flake-like patterns. This ornamentation is close 

 to that of Xyris, in the writer's opinion, although Achlyphila is like the other 

 two genera in the nonaperturate condition. The most logical explanation of 

 the exine in Abolboda and Orectanthe seems to be that differentiation into two 

 types of elements — minute pila and large spines or knowbs — has taken place ; 

 this differentiation most likely would have started from a condition like 

 that found in Achlyphila. The relatively thick nexine, lacking in lipophilic com- 

 pounds, offers a common basis among the genera. More study of Xyris pollen 

 is required before a definite phylesis can be suggested, but the above inter- 

 pretations appear most likely at the present moment. 



The reader will note that the taxonomic conclusions expressed above bear 

 a very close resemblance to those of Maguire, Wurdack, et al. (1958, 1960). 

 The writer agrees with these authors in their conclusion that the four genera 

 of Xyridaceae are highly distinctive, but show more common resemblance than 

 any resemblance of any one to a genus of another family. The writer was 

 pleased to find, in addition, that his anatomical material lends such clear-cut 

 support to specific and even subspecific (Abolboda macrostachya) designations 

 of these authors. 



Literature Cited 



Arber, Agnes. 1925. Monocotyledons. 1-258. 



Carlquist, S. 1958. Anatomy of Guayana Mutisieae. Part II. Mem. N. Y. Bot. Gard. 10: 

 157-184. 



Cheadle, V. I. The occurrence and, types of vessels in the various organs of the plant in 



monocotyledons. Am. Jour. Bot. 29: 441-450. 

 Erdtman, G. 1952. Pollen morphology and plant taxonomy. 1-539. 



Maguire, B., Wurdack, J. J. & collaborators. 1958. The botany on the Guayana Highland — 

 Part III. Mem. N. Y. Bot. Gard. 10: 1-156. 



. 1960. The botany of the Guayana Highland— Part IV. Mem. N. Y. Bot. 



Gard. 10: 000-000. Pages to be supplied in proof. 



