354 The Ohio Naturalist. [Vol. V, No. 8, 



The subject has proved very interesting because of the large 

 number of closely related plants which have already been studied 

 and the accumulated literature which was easy of access either 

 in the original publications or through brief reviews and abstracts. 

 The writer became thoroughly familiar with her own material 

 before making any comparisons in order to avoid having pre- 

 conceived ideas of what ought to be expected. 



Material for study was collected at Licking Reservoir in 1901 

 by Professor J. H. Schaffner and at Sandusky Bay, Lake Erie in 

 the summers of 1902-1903 by the writer. The usual methods of 

 killing, imbedding, sectioning and staining were employed. 

 Thickness of the sections varied from 8-20 microns the older 

 material being cut thickest. 



The development of the carpel is almost identical with that 

 of Ranunculus abortivus as described by E. A. Bessey (1). The 

 rounded pyramid of the receptacle first appears from which 

 numerous conelike projections arise (Fig. 1). Those nearest the 

 base develop into the stamens. Near the summit of the receptacle 

 the arrangement of parts is spiral but approaches the cyclic 

 among the outer stamens. The number of stamens found by 

 actual count varied from 17-21 while the number of carpels was 

 approximately half as great. A lamina or flap develops from the 

 distal side of the young carpel enveloping the inner portion 

 which begins to grow away from the receptacle (Fig. 2). This 

 lamina thins out as it meets the axillary placenta and traces of 

 the integuments can be seen (Fig. 3). As the nucellus develops 

 it describes an angle of 180° and when the gynoecium is mature 

 the tip of the nucellus is directed downward while the opening of 

 the micropyle is towards the receptacle. (Fig. -1). Only a single 

 integument develops. The outer cells of the integument nearest 

 the placenta are large and glandular and seem to function in 

 conducting the pollen tube to the micropyle (Fig. 5). After the 

 closing of the carpel an elongated style develops having linger 

 like, glandular cells on the stigma wdiich afford a lodging place 

 for the pollen. 



The microsporangium develops a plate of four or five hypo- 

 dermal archesporial cells which divide by periclinal walls to 

 form primary wall and primary sporogenous cells (Fig. 6). The 

 primary wall cells then divide and the inner cells develop into 

 the tapetal layer (Fig. 7). The outer cells may divide once or 

 twice forming two or three distinct layers between the epidermis 

 and the tapetum (Fig. 8). The layer next to the epidermis forms 

 the endothecium with thickenings in the angles of the walls, 

 exactly as were found in the endothecium of R. delphinifolius. 

 Further divisions by anticlinal walls occur in both tapetal and 

 wall layers and later the tapetum becomes binucleate by kary- 

 okinesis, without forming walls, instead of by fragmentation of 

 the nucleus (Fig. 10-11). 



