T. Holm — Dirca Palustris. I'TT 



Art. XII. — Dirca palustris L. A morphological study; 

 by Theo. Holm (with seven figures drawn from nature 

 by the author). 



The ThymelaeacecB is a small family comprising only 36 

 genera with about 360 species according to Bentham and 

 Hooker. Most of the species are natives of South Africa, 

 the Mediterranean region and Australia ; Dirca, however, 

 is confined to North America, and only two species are 

 known : D. palustris L, and D. occidentalis Gr., the former 

 widely distributed from Ontario and Quebec southward to 

 Florida; the latter is a native of California, and is 

 described as follows : 



Dirca occidentalism 



' ^ Foliis ovalibus basi rotundatis ; squamis involiicri extus albido- 

 villosis; floribus fructibusque fere sessilibus; perigonio breviter 

 infundibuliformi-tri-qnadrilobo. California, on the Oakland hills 

 (perhaps in ravines), Dr. I. M. Bigelow (D. palustris Torr. Bot. 

 Whippl. p. 77. non Lmn) . A second species of this before mono- 

 typical genus is of peculiar interest. The Californian Dirca was 

 collected twenty years ago by Dr. Bigelow, ^'with flowers and 

 young fruit" according to Dr. Torrey, but there are only 

 vestiges of the former in my specimens. If they had been in 

 good condition, Dr. Torrey would have noticed the characters 

 of the species, which are now manifest. The white hairs of the 

 floral bud-scales may not be constant; for in D. palustris they 

 are occasionally pale ; but the deep and rounded lobes of the more 

 funnelform calyx are characteristic, being from one-fourth to one- 

 third the length of the tube. Very commonly there are only three 

 sinuses, one lobe being broader and emarginate. The stamens are 

 uniformly eight. The original species may be thus characterized : 



Dirca, palustris L. Foliis basi angustioribus ; squamis involu- 

 cri nigricanti-villosis ; floribus pi. m. pedicellatis ; perigonio tubu- 

 loso-infundibuliformi margine tantum repando. Nova Scotia to 

 Lake Superior and Lake of the Woods, and southward to Florida 

 along the AUeghanies. " 



Internal Structure of the Vegetative Organs of Dirca 



palustris. 



The Root. — In mature specimens the roots are quite 

 thick, very soft, and of a yellowish-brown color. A homo- 



^Gray: Characters of new genera and species of plants. (Proceed. Am. 

 Acad, of Arts and Sc, Vol. 8. Boston, 1873.) 



Am. Jour. Sci. — Fifth Series, Vol. II, No. 9. — September, 1921. 

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