No. 629] FLOWER NUMBER IN VERNONIA 527 



Michigan and adjacent Ontario, it is typically a species 

 of moist, cleared, uncultivated bottom-lands along the 

 rivers and lakes and occasionally is found in low woods 

 as well, where it is taller and more slender, with rela- 

 tively lax, irregular, few-headed inflorescences. Judged 

 from herbarium evidence from all parts of its range, the 

 mode of its flower-number seems to be 34. Since flower- 

 numbers deviate more freely from the Fibonacci series 

 in the higher numbers and since the species has such a 

 wide range and such a wide variation in its habitat, it 

 may naturally be expected that it will present a wider 

 variation in flower-number than many other species of 

 restricted range and habitat and with smaller heads. 



The inflorescence of the species may be described in 

 some detail. It is strictly cymose. The main axis of the 

 plant is unbranched and rises to a height of one to two 

 meters. The lower nodes bear full-sized foliage leaves 

 and are separated by internodes of fairly uniform length, 

 while the upper internodes are abbreviated and bear re- 

 duced or bracteal leaves only. The main axis terminates 

 in a single head on a short peduncle, and this head is the 

 first, or among the first, to bloom. From the axils of the 

 uppermost leaves branches appear which are in turn 

 terminated by a single head on a longer peduncle, which 

 therefore overtops the primary head. The next nodes, 

 subtended by larger leaves, bear short simple leafless 

 clones of 2-5 heads. Below these, leafy branches appear 

 from the lower nodes, and these bear single primary ter- 

 minal heads, axillary heads on longer peduncles, and 

 simple cymes in the same order in which they appear at 

 the summit of the main axis. The uppermost of these 

 leafy branches, since they arise relatively near tlie sum- 

 mit of the plant, als.^ ovei-io|. ihc main axis and with it 

 produce a nmiT m- los tlattencd or dcpn^sed eorymbi- 

 form cluster. Tlie lowci' lateral Irat'y l)i-aneh.'< aiv suc- 

 cessively shorter, bear U'W^-v heads whieh lilixmi later, 

 and tend to produce in conjunction with the up].cr ones 

 a more or less cylindrical cluster. l''inall\. tlu^ lowest 



