TWENTY-FOUBTH ANNUAL MEETING. 25 



I. — Vabiations in Size. 



It would be impossible to bring together all the illustrations that might prop- 

 erly be included under this head; and I shall only refer to a considerable number 

 of those cases that furnish the most positive proof of our proposition. 



CEnothera serrulata Nutt. — And its forms should probably be placed first in this 

 list of illustrations. It is well distributed over by far the greater portion of the 

 United States, accompanied by a number of described varieties and a limitless 

 number of intermediate forms. There is great variation in the size of the entire 

 plant and of the leaf and flower, the flowers ranging in size from nearly two inches 

 across to a little more than half an inch. Its largest representatives are found east- 

 ward, as a rule, and it becomes smaller farther and farther into the sandy districts of 

 the southwest and on the summits of rocky hills. I have myself found at least three 

 distinct forms of this species, with many intermediate grades. The largest form 

 was noted on the prairies of the Pottawatomie country, in central Indian Territory; 

 the smallest on the gypsum hills and in sandy districts of western Indian Territory 

 and Panhandle, Texas, and a form intermediate in various places in Kansas and 

 the other two countries first named. Two large-flowered varieties are mentioned in 

 the manual of western Texas plants* as occurring in that region. 



Paniculn virgaium L. — ^One of our most common and widely diffused American 

 grasses — is simply invariable in its variableness. It varies in the general coarseness 

 of the plant and the size of the spikelets. Yet, it may be noted that this species 

 has but one published North American variety (according to Oyster's "List"); and 

 it should be remarked here that one cannot always determine upon the amount of 

 variations of a particular species from the number of its described varieties, as the 

 variations, although quite numerous and extremely diverse, may not be sufficient in 

 degree for the establishment of a new variety. 



Grinclelia squarrosa Dunal — Presents considerable variations in the size of leaf 

 and flower head. Its variety grandiflora Gray is well known. 



Tradescantia pilosa Lehm. — Very wide ranging; grows gradually, but considera- 

 bly, smaller, from eastern Kansas to New Mexico. 



Other common species that vary in size may be noted, as follows: 



Engelmannia pinnafifida T. <fe G. — Grows smaller to the westward. 



Chrysopsis villosa Nutt. — Varies in size" of head, and of the whole plant. 



Petalostemon violaeeus Mx. — Varies extremely, principally in size of heads. A 

 form, seemingly constant, found in Morton county, Kansas, is probably var. tenuis 

 Coulter.t 



Petalostemon candidus Mx. — Varies also as the last. 



Aplopoppus spinulosus DC. — Varies in size of heads. 



Then there is the great host of asters and solidagos that vary so much that the 

 varieties, and even some species, with their multitude of intermediate forms, pre- 

 sent almost inextricable confusion. Among them may be mentioned: 



Aster multijlorus Ait. 



A. ericoides L. 



A. salicifolhts (Lam.?) Ait. 



Solidago canadensis L. with several varieties. 



S. missouriensis Nutt. and numerous varieties. 



S. serotina Ait. 



S. occidentalis Nutt., etc. 



All these are extremely common and wide ranging. 



* J. M. Coulter, "Manual of the Phanerogams and Pteridophytes of Western Texas," page 117, No. 23. 

 t Coulter — "Manual of the Phanerogams and Pteridophytes of Texas," Polypetalse, p. 79, No. 4. 



