Febeuaky 7, 1908] 



SCIENCE ■ 



207 



eight species; estival, Juue 1 to about July 

 7— twenty-one species; serotinal, July 7 to 

 about August 7— thirteen species; au- 

 tumnal, August 7 to about September 21— 

 twenty-two species. The prairie elements 

 show a marked grouping into layers which 

 correspond with the floral asj^ects. Over- 

 topped by the autumnal, the sublayers are 

 successively those of the serotinal, estival, 

 vernal and prevernal. There is a marked 

 distinction in the chresard of base, slope 

 and crest in the prevernal, which becomes 

 less marked in the subsequent aspects, ap- 

 proaching equality in the autumnal. As 

 a result the floral covering shows a cor- 

 responding difference upon base, slope and 

 crest in earlier aspects; the influence of 

 position gradually declines, the floral cover- 

 ing presenting a striking similarity over 

 the entire formation in the autumnal. 



New or Noteworthy Peronosporales: Guy 



"W. Wilson. 



In the course of a monographic study of 

 the Peronosporales several problems in 

 specific limitations have arisen, some of 

 which have been solved and are discussed. 

 To these notes are added the description 

 of two new species of Albugo and notes on 

 the distribution of Phytoplithora thalictri 

 and Peronospora floerkeae, both of which 

 are rare species. 



Both Albugo triantherce and A. clado- 

 tliricis were described from Las Cruces, 

 New Mexico, the former occurring on 

 Trianthera, the latter on Cladothrix. 

 Both are rather closely related to A. bliti, 

 but are distinguishable by conidial char- 

 acters. The oospore of A. trianthercB is 

 also quite characteristic, while that of A. 

 cladothricis is unknown. Of the four 

 other species discussed, Peronospora cypar- 

 issicB, P. rumicis and P. hyoscyami are to 

 be dropped from the list of American 

 species, the first being a mistaken deter- 

 mination of P. eupJiorbice, while the other 



two represent European species with Amer- 

 ican cognates. P. rumicis becomes P. poly- 

 goiii and P. hyoscyami becomes P. nico- 

 tians, a species heretofore reported only 

 from South America. P. arborescens must 

 also be added to our flora, having been 

 collected in Colorado on Argemone, but 

 erroneously reported vinder the name of 

 P. corydalis. 



Notes on Cleistogamy of Grasses: Agnes 

 Chase. 



I. The genus Triplasis is found to pro- 

 duce late in the season cleistogamous spike- 

 lets in small panicles wholly or partly in- 

 cluded in the sheaths; specimens of T. 

 purpurea (Walt.) Chapman, collected in 

 October, 1907, show a second form of 

 cleistogene, larger than the others, solitary 

 and sessile at the base of the prophyllum. 



II. Amphicarpon amphicarpon (Pursh) 

 Nash was collected in October, 1907, with 

 perfect grains in the aerial spikelets as well 

 as in the subterranean cleistogamous ones. 



Mutations of Rudbeckia hirta: W. J. Beaij. 

 Dr. W. J. Beal, of Michigan Agricul- 

 tural College, during the past five years 

 has selected from many thousands of 

 plants, certain peculiar foi'ms, sports or 

 mutations, flowers of some of which he 

 exhibited : 



1. A specimen with wide ray flowers, the 

 head four inches across. 



2. A large head of flowers with the base 

 of each ray dark purple. 



3. A large head with fourteen ray 

 flowers, each quilled or narrow for one 

 fourth inch at the base. 



4. A head in which all the rays were 

 tubular or quilled. 



5. A head with rays very light yellow. 



6. The rays twisted. 



7. A very small head with rays about one 

 fourth inch in length. 



