62 



species may in some places or at some seasons appear very conspicu- 

 ously. A striking example of this was given by Linum sulcatum, 

 which was observed only on one sand-hill near Oquawka, and w^as so 

 local that it did not appear in any of the quantitative studies made 

 there. The plant has very slender erect unbranched stems, and dur- 

 ing the first days of July was hardly noticeable. A few days later 

 the flowers appeared and brought the plant at once so much into evi- 

 dence that it might have been wn-ongly considered a characteristic 

 member of the consocies. 



TabI^E I. — Fl^ORISTlC COMPOSITION OF TEN QUADRATS IN THE Leptoloma COg- 



nafum consocies, oouawka area. 



Iveptoloma cog-natutn 

 Paspalum setaceum 

 Panicum Scribnerianum 

 Bouteloua hirsuta 

 Cyperus filiculmis 

 Carex Muhlenberg-ii 

 Rumex Acetosella 

 PolyL'onum tenue 

 Silene antirrhina 

 Cassia Chamaechrista 

 BaptLsia bracteata 

 Amorpha canescens 

 Polyg-ala incarnata 

 Oenothera rhombipetala 

 Verbt-na stricta 

 Monarda punctata 

 Hedeoma hispida 

 Ivinaria canadensis 

 Pentstemon hirsutus 

 Ruellia ciliosa 

 Specularia perfoliata 

 Erig-eron ramosus 

 Antennaria sp. 

 Ambrosia psilostachya 

 Senecio Balsamitae 



xxxxxxxxxx 



X X - X X X - X X - 



- X - - - X X - - - 



xx-xxx-xxx 

 - - X X - 



- - - - . - - . X - 



- xxxx - xxxx 



X - - - X 



- - X - - - X - - - 



- X X X - - X X - - 

 X X X - X - - X - X 



- X X - X - - - - X 

 X - - - - 



- - - X - - X - - X 

 X X - X - - X X X - 

 X - X X - X X - - X 



------ X - X - 



. - X ------ - 



----- X - - X - 



XXXXXXXXXX 



- X - - ----- - 



- - - X X X X - - X 

 . X - ----- - 



XX - XXXXXXX 

 -..--. X - - . 



A series of counts (Table I) were made at Oquawka, in the best 

 example of the consocies observed (near the site of Plate I, Fig. 2), 

 to determine the relative frequency of the secondary species. These 

 counts record the presence or absence of the species in each of ten 

 quadrats two meters square, extending in a continuous strip through 



