166 MISSOURI BOTANICAL GARDEN. 



r 



ginianaj specimens of Rosa blanda and R. humilis not being 

 uncommon. 



In spring the ground cover is composed of occasional spe- 

 cimens of Delphinium tricornej Arahis ludoviciana, Draha 

 cuneifolia^ Arenaria i)atulaj Polygala veriicillata^ Astragalus 

 mcxicanuSj Floustonia purpurea, Camassia Frascriy Nothoscor- 

 duni striatum and others, Cacalia tuberosa makes its ap- 

 pearance in the spring, as does Silphium iulegrijoliumj to 

 remain throughout the summer and fall. Opuntia Rafin- 

 esquii and Agave virginica are typical here. An excellent 

 illustration of the latter species in this locaHty is given by 

 Miss Mulford."^ The grasses ordinarily met with are Boute- 

 loua raccmosa, Danthoiiia spicata and Panicum depauperatum. 



The early summer presents the largest number of species. 

 The principal plants are Silene antirrhina^ Ascyrum Crux- 

 AfidreaCj Hypericum nudicaule, Crotalaria sagii talis , Les- 

 pcdeza capitata, Peialostcmon violaceus and P. candidus, Gaura 

 biennis, Polytaema Nidtalliij Pimpinella integerrima, Thaspium 

 aureumj and Blephilia ciliata. In autumn these arc largely 

 replaced by Compositae, such as Aster laevis and A. oblongi- 

 foIiuSy Eupatorium altissiv2U77i, SoUdago petiolaris and S. 

 rigida. Gerardia tenuifolia is frequent at this tunc as are 

 Andropogon furcatus and A. scoparius. Pteris aquilina is 

 common throughout the year, 



Sinkholes- 



As indicated above, sinkholes in the deciduous forest may 

 be either dry or wet. Where dry, i. e. where a drainage 

 system is present, they harbor plants w^hich are usually re- 

 ferred to as appreciating a well drained soil (plate 13). Hy- 

 drastis canadensis, Oxalis violacca, Polygonatum giganteum, 

 Smilacina racemosa, Arisaema Dracontium and A, triphyllum 

 occur here in greatest abundance. They form the most im- 

 portant portion of the flora of sinkholes during the spring 

 and summer months, together with Sanicula marylandicay 

 Spiraea Aruncus and occasional ferns such as Adiantum 

 pedatum, Aspidium acrostichoideSy and Cystopteris fragilis, 



Mulford, A. I. A Study of the Agaves of the United States. Rept. 

 Mo. But. Gard. 7. pL 26, ISDG. 



