1922] 



PFEIFFER MONOGRAPH OF THE ISOETACEAE 99 



Oceanica proves very rich in forms, with three each in Aus- 

 tralia (/. Drummondii, I. Muelleri, and /. tripus) and Tasmania 

 (7. Gunnii, I. elatior, and /. humilior), and two allies in New 

 Zealand (/. alpina and /. Kirkii}. 



Floristic Relations. Some of the Mediterranean forms, as 7. 

 velata, adspersa, Boryana, tegulensis, and tenuissima and /. 

 velata Perralderiana, show a very close relation as though orig- 

 inating from a single stock, which may be referred to as the Eur- 

 African stock. No other morphological group as large as this 

 is found in so limited a geographical region. The two New 

 Zealand species, 7. alpina and 7. Kirkii, show evident relations 

 to each other. But associated morphologically with these eight 

 forms are many others in widely distant stations, as 7. cubana of 

 Cuba, 7. Schweinfurthii of Central Africa, 7. Orcuttii of southern 

 California. Obviously it is impossible to determine any basic 

 forms here. 



In what might be termed the Echinatae group, one finds many 

 reports of 7. echinospora itself in Europe, the closely related 7. 

 Braunii in our northern territory (the two probably bridge the 

 Atlantic Ocean in the Arctic islands), and a variety in Japan 

 which presents a difficulty in the attempt to ascertain to which 

 it is the more closely related. There are representatives of this 

 group also along the west coast of North America, up to Alaska. 

 Obviously there is a more or less continuous northern band about 

 a large part of the known territory. Discontinuity may be due 

 to lack of present forms or to lack of knowledge of such forms. 



The other morphological groups show rather a similar situa- 

 tion to the first-mentioned group, with representatives scattered 

 in north, south, east and west hemispheres. 



It may be noted that the distribution of diverse species, of a 

 remarkably conservative genus, is striking in the number of in- 

 sular and coastal region forms which appear. 



MATERIAL EXAMINED 



The present monograph was suggested to the writer by Dr. 

 J. M. Greenman, under whose guidance the work has come to 

 completion at the Herbarium of the Missouri Botanical Garden. 

 To him especial thanks are due for encouragement, suggestion, 

 and advice in the progress of the problem. The writer is indebted 



