154 TRANS. OP THE ACAD. OF SCIENCE. 



April 15, 1861. 



The President, Dr. Engelmann, in the chair. 



Twelve members present. 



Letters were read as follows : 



Hon. Samuel D. Bell, Manchester, N. H., March 29, 1861, concerning 

 Transactions ; Royal Geograph. Soc. London, Jan. 15, 1861, — Geological 

 Soc. of London, Nov. 7, I860,— British Museum, Oct. 26, I860, acknowl- 

 edging receipt of the Transactions of the Academy ; A. F. Bandelier, Jr., 

 Highland, III., April 3, 1861, communicating meteorological observations 

 at Highland. 



The following publications were received : 



Report on the Geology and Agriculture of Mississippi, by E. W. Hil- 

 gard, State Geologist, from the Author; Ueber die Spuren eigenth. Erup- 

 tionserzes des Dacbsteingeb. Wien, 1860, von Prof. Ed. Suess, from the 

 Author; Bulletin of the Amer. Ethnol. Soc. New York, Vol. I., Sept. to 

 Jan. 1861, from the Society; Bull, de la Soc. Imp. Zool. d r Acclimatation, 

 Paris, T. VIII., No. 2, 1861, from the Society; Proc. Boston Soc. Nat. 

 Hist., Vol. VIII., March, 1861, and Index to Vol. VII. ,from the Society. 



Dr. Shumard presented a series of land shells from the 

 Quaternary deposits of Washington Co., Texas. 



Dr. Engelmann spoke about the dimorphism of Draba bra- 

 chycarpa, and exhibited living specimens of this plant illus- 

 trated by drawings. 



This humble white flower is at this season very abundant on the grassy 

 hills about town, associated with Draba Caroliniana, the pretty Housto- 

 nia minima, with Androsace occidentalis, Plantago pusilla, Ranunculus fas- 

 cicidaris, Myosurus minimus, and the completely naturalized Capsella. In 

 ordinary or in wet springs the flowers are all regularly formed and compa- 

 ratively large, having a diameter of about 2 lines ; in very dry springs, how- 

 ever, such as the present one, a form with very inconspicuous flowers be- 

 comes common, which in isolated specimens in the herbarium might be 

 taken for a distinct species, but, studied on its native hills in thousands of 

 specimens, clearly proves to be nothing but a depauperate or abortive 

 state and not even a clearly defined variety. 



During a late excursion to our commons in company with Dr. Hilgard, 

 he ascertained that on the northern slopes of hills and sinkholes, and near 

 the edge of ponds, the plant had the ordinary appearance, but on the sunny 

 and dry or even arid southern slopes not a single one among the thou- 

 sands of specimens could be found the flowers of which were not quite 

 inconspicuous ; in intermediate situations the size and organization of the 

 flowers were also intermediate. 



These incomplete flowers are smaller in all their parts than the regular 

 ones ; the sepals are erect and rather persistent ; the petals always shorter 

 than the sepals, but variable in size, shape and number, or even entirely 

 absent; the stamens always abortive and often reduced in number; the 

 ovary shorter but fertile. 



The petals ordinarily broadly obovate-spatulate, retuse, over 1 line 

 long, are here linear-spatulate, entire, emarginate or bilobed, J-i line 

 long, 2 or 4 in a flower, often of unequal size in the same flower, or en- 

 tirely absent. The slender filaments bear a bilobed cellular head, often 

 not more than 0.05 line long, representing the anther, but without any 

 regular structure. He found in single flowers 4, and often 5 or 6 of them, 

 without petals, or associated with 2 or 4 rudimentary petals. It appears 

 that in some incomplete tetrandrous flowers the pairs of stamens adhere 



