J26 
IOWA ACADEMY OP SCIENCE 
CONCLUSION. 
The foregoing studies suggest the following conclusions: 
1. That the flora of the prairie is essentially xerophytic, dif- 
fering from the desert flora chiefly in the degree of modifica- 
tion for protective purposes. 
2. That these xerophytic adaptations are to some extent va- 
riable in the same species. 
3. That they vary in different species in much the same man- 
ner, though usually in lesser degree, as the xerophytes of the 
desert. 
Botanical Laboratory, 
State University op Iowa. 
EXPLANATION OP PLATE XX. 
Leaf sections; 
a — Cutin. 
b — Stoma, 
c — Trichomes. 
d — Bulliform cells, 
e — Water storage parenchyma. 
The shaded cells are palisade cells. 
The following species are represented: 
Fig 1. — Dalea alopecuroides Willd. 
Pig. 2. — Amorpha canescens Pursh. 
Pig. 3. — SoUdago nemoralis Ait. 
Pig. 4. — Lactwoa ludoviciana (Nutt.) Ridd. 
Pig. 5. — Oxytropis Lam'berti Pursh. 
Fig. 6. — Solidago speciosa var. angustata T. & G. 
Pig. 7 — Grindelia squarrosa (Pursh) Dunal. 
Pig. 8. — Panicum Scrihnerianum Nash. 
