1 889. J BOTANICAL GAZETTE. 1 45 



Fig. 11. Tangential section of leaf of Avena sativa cutting a com- 

 pound sorus of P. coronata midway between spore-bed and epidermis : 

 a, teleutospores in cross section ; 6, cells of fibro vascular bundle ; c,inter- 

 sorial stroma in cross-section. Section 5 p thick. X 350. 



Fig. 12. Teleutospores of P. rubigo-vera on Triticum vulgare from 

 Ellis' "North American Fungi" No. 1471, showing variations in size and 

 form upon the same host : a, b, type spores ; c and d, spores bearing short 

 points at apices ; /, a one celled spore. X 350. 



Fig. 13. Teleutospores of P. coronata Cda. on Avena sativa from one 

 host : a and 6, type spores ; e, e and /, forms often found ; d, truncated 

 spore ; g, two mesospores and a teleutospore from corner of sorus. X 3oO. 



Indiana Experiment Station, Lafayette. 



Achenia of Coreopsis 



J. N. ROSE. 



(WITH PLATE XVI.) 



Coreopsis shows as great a variety of achenia as any ge- 

 nus of Composite, but thev are hard to define. 1 .hey maj 

 be flat or somewhat 4 -sided, straight or curved, orbicular to 

 linear-oblong in outline, glabrous to pubescent, winged or 

 wingless, with entire or laciniate-toothed margin, apex trun- 

 cate or emarginate, pappus of two awns (sometimes moiej 

 or of teeth o? scales; these generally upwardly hispid (often 

 naked), or all these wanting. The genus is not clearly sep- 

 arated from Bidens. for while the one is said to have its a ns 

 always upwardly hispid, and the other downwardly hispid, 

 several species in each hybridize freely and break down this 

 distinction. While the genus possesses such a range !Ol n u u 

 structures, and by this alone one can not ahva y% dis ^f^f 

 species as now defined, it enables natural groups ot a tew spe- 

 cies to be easily formed .and most of these can then be sepal ated 

 by leaf characters. In some cases it seems questionable wheth- 

 er these sub-divisions should be made, for thev embiace so 

 many intermediate forms that no line can be clearly drawn 

 u~* - .- tvt .^ *. hoe v»ppn made in this papei to 



between them. No attempt has Deen mauc .» »«- r-r--" 

 combine species, with the belief that Dr. Gray in ^Synop- 

 tical Flora has given the most satisfactory arrangement* hat 

 can now be mlde. His lineal order has been followed in 



