152 STUDIES IN GEOLOGY, No. 4 



The only modern ecological treatment of this flora is in the 

 important paper by Herzog x published in 1910. This has 

 proved to be very helpful, but Herzog's stay in the country 

 was short and the identified material which he collected 

 included only about 600 species of vascular plants, which 

 probably represent less than 10 per cent of the whole flora. 

 Moreover he did not visit the most interesting part of Bolivia, 

 namely the Yungas, lying east of the Cordillera Real and 

 north of the Sierra de Cochabamba, which is the region of 

 most importance in studies of the Tertiary floras of the 

 Andean region. 



The systematic enumeration of the Rusby and Bang col- 

 lections contains a wealth of information, but the arrange- 

 ment is systematic and not geographical, the localities are 

 not given with sufficient precision, nor are the altitudes 

 reported in many instances, so that in the particular features 

 most significant for an interpretation of the Pisllypampa 

 fossil flora, the data are wanting. 



The total number of recognizable forms at Pisllypampa is 

 limited to 20 species. It is unfortunately true that in collec- 

 ting from difficult and inaccessable localities such as Pislly- 

 pampa one is very much limited for time and the collections 

 will be as a rule correspondingly poor. At the same time, in 

 describing materials from such remote Andean localities that 

 may never be visited again, it has seemed important not to 

 ignore the most fragmentary material if it was at all capable 

 of yielding any information. This is my reason for attempt- 

 ing the identification of some specimens, which, if they had 

 come from the United States, I would have lain aside and 

 waited for subsequent collections of more complete material. 



The twenty species recognized include three ferns, two 

 monocotyledons and fifteen dicotyledons. The most abun- 

 dant individually are the fern species of Goniopteris, the 

 moraceous species of Coussapoa and the fruits of Saccoglot- 



1 Herzog, T., Pflanzenformationen Ostbolivias. Engler's Bot. 

 Jahrb. Bd. 44, pp. 346-405, 1910. 



