Nov., 1902.] Ohio Plants with Dissected Leaves. 315. 



light, differences in nutrition, temperature, and so forth, which is 

 the commonly accepted explanation for the form of submerged 

 leaves. This explanation, liowever, is too general to be entirely 

 satisfactory. In this connection, McCallum* has been conducting 

 experiment with Proscrpiiiaca paliistris, at the Hull Botanical 

 Laboratory. These experiments seem to indicate that the hereto- 

 fore accepted explanation based upon diminished light, nutrition^ 

 and so forth, will not hold good. It appears that the only constant 

 factor in all cases where the water form develops is the checking 

 of transpiration and the increased amount of water in the proto- 

 plasm. Whatever the inciting cause may be, it seems that this 

 condition brings out a certain set of hereditary characters while 

 the absence of it produces a dift'erent set ; just as a root in the soil 

 is a typical root, but when growing above the ground may some- 

 times produce buds and leaves. 



IN WATER. 



Ceratophyllvini demersuiii — in ponds and slow streams. 



Ranunculus delphinifolius — in ponds. 



Batrachium tricophylluni— in ponds and streams. 



Batrachium divancatum — in streams. 



Roripa Americana — in lakes and slow streams. 



Podostemon ceratophj-llum— in shallow streams. 



Floerkea proserpinacoides— in marshes and along rivers. 



Proserpinaca palustris — in swamps. 



IMyriophyllum spicatum— in deep water. 



Myriophyllum verticillatum — in both deep and shallow water. 



Myriophyllum tenellum — on sandy bottoms of ponds and streams. 



Myriophyllum heterophyllum — in ponds. 



Conioselinum Chinense— in cold swamps. 



Hottonia inflata — in shallow stagnant ponds. 



Utricularia vulgaris — in brooks and ponds. 



Utricularia intermedia — in shallow water along margins of pools and 



ponds. 

 Utricularia minor — in shallow ponds and bogs. 

 Utricularia gibba — in shallow water or in mud on borders of ponds and 



pools. 

 Bidens Beckii — in ponds and streams. 



ON DRY LAND. 



Delphinium consolida — in waste places. 



Delphinium Carolinianum — on prairies and open grounds. 



Bicuculla cucullaria — in woods. 



Bicuculla Canadensis — in rich woods. 



Capnoides flavulum— in rocky woods. 



-W. B. McCallum. On the Nature of the Stimulus causing the Change of Form and! 

 Structure in Piosei piiiaca palnsliis. Bot. Gaz.j^: 93-108, 1902. 



