MICHIGAN ACADEMY OF SCIENCE. 167 



CONTRIBUTIONS TO THE BOTANY OF MICHIGAN NO. 14. 



BY OLIVER ATKINS FARWELL.* 

 MICHIGAN N0VP:LTIES. 



When any botanical field is, for the first time, subjected to an in- 

 tensive study, it will produce a number of new and interesting forms, 

 at least to the student of systematic botany. During my field work 

 in and around Rochester, Oakland Co., Michigan, in 1914, a number 

 of such were discovered some of which form the basis of this paper. 

 Two species, MiteUa diphylla and Apocynum Farwellii, evidently in 

 that condition which DeVries calls "Mutable", may be mentioned as 

 especially illustrating one wa}^ of producing what he terms "elementary 

 species." This is by way of suppression or obliteration of some part of 

 the plant body. That the former species is in a mutable condition is 

 more apparent as two variations have already been described and 

 named, which are not due to a suppression or reduction of any part of 

 the plant body. 



The variations already named include forms with a third leaf on the 

 scape situated between the normally opposite nearly similar leaves and 

 the infloresence and another wherein the leaves are long petioled. 

 The form I have found has but one leaf on the scape. Here one of the 

 normally opposite leaves has been suppressed; the species wherever it 

 grows is found in large patches, and in such patches where this form 

 with, one leaf occurs, one will always find a series of individual plants 

 that will show a complete gradation from the normal to this form; 

 that is, with one leaf gradually getting smaller, while the other remains 

 normal, until the blade has entirely disappeared and then a similar 

 shortening of the petiole until there is no evidence on the surface of the 

 scape of a second leaf. I have seen plants in which the leaf blade had 

 been reduced to the size of a minute bract, perhaps 1-16 of an inch in 

 length, and others on which the only indication of a second leaf was a 

 small mucro of similar length and one that even had a flower opposite. 

 Evidently the flower was of axial origin but there was no indication 

 whatever of the subtending leaf. It may also be remarked that an 

 axillary flower is quite an unusual condition in this species. 



The other plant is one of our dogbanes. When first collected I had 

 referred it to Apocynum pubescens R. Br., but Dr. E. L. Greene, of 

 Washington, D. C, considered it distinct and has named it Apocynum 



•Department of Botany, Parke, Davis & Co., Detroit, Micli, 



