FLORAL SUCCESSION IN THE PRAIRIE-GRASS FORMA- 
TION OF SOUTHEASTERN SOUTH DAKOTA 
SEROTINAL AND AUTUMNAL FLORAL ASPECTS 
CONTRIBUTIONS FROM THE HULL BOTANICAL LABORATORY I17 
LeRoy HarRis HARVEY 
(WITH FOUR FIGURES) 
Serotinal floral aspect 
Climatologically and florally the serotinal is perhaps the most 
distinctly demarked of the aspects. The climatological changes 
which set it off from the estival are quite generally appreciated, while 
the general blooming of the pioneer sod-formers during the early 
Part of July with the accompanying serotinal bloomers no less dis- 
Unctly marks it in a floral way. 
One records now less dissimilarity in aspect and tone on crest, 
slope, and base ; the more open association, however, still marks the 
‘rest. The tone is determined by the dull-greenish vegetative stalks 
of Solidago rigida and Helianthus Scaberrimus, which occur copiously 
throughout the formation. It is relieved locally on lower slopes by 
the yellow of Ratibida columnaris and on upper slopes by the blue 
of Verbena stricta and the canescence of Amorpha; while Meriolix 
Serrulata, Brauneria pallida, Potentilla Hippiana, Erigeron ramosus, 
Polygala alba, and Euphorbia marginata, all of which extend over 
m the estival, are less influential. A few conspicuous forms are 
added In this aspect, but never of sufficient abundance to strongly 
nay the dull green of the tone given by the leafy stems of Soli- 
4g0 and Helianthus. 
The Seneral flowering of A gropyron occidentale, Bulbilis dacty- 
a the Boutelouas, together with Kuhnistera purpurea and K : 
POoaEe, distinctly marks the inception of the serotinal aspect, which is 
terized by the gradual appearance of few but conspicuous 
Rte and the attainment of maximum flowering of late estival 
» Tather than by the addition of numerous forms as in the 
an [Botanical Gazette, vol. 46 
