NO. I S.MITIISOXIAX EXPLOR.\TIONS, I919 4I 



In the vegetation there are represented four of the Hfe zones 

 recognized by biologists. The Transition Zone is inchoated on the 

 west slope by smah areas of yeUow pine timber, and east of the Park 

 are the prairies of the Blackfoot Indian Reservation, which extend 

 also within the Park boundaries along the stream valleys. The plants 

 here are chiefly herbs, with a few shrubs, and they belong" mostly to 

 species which have a wide distribution over the Great Plains. By 

 far the largest portion of the Park is covered with the characteristic 

 vegetation of the Canadian Zone, which is the heavily forested area. 

 Above the Canadian Zone, around timber line (6,000 to 7,500 feet), 

 lies a narrow belt belonging to the Hudsonian Zone. The trees here 

 are mostly low and stunted, and their branches frequently lie pros- 

 trate upon the ground. Above this belt, and occupying the highest. 

 exposed slopes, lies the Arctic-Alpine Zone, whose vegetation is 

 composed chiefly of small herbaceous plants, with a few dwarfed 

 shrul)s. mostly willows. Many of the species of this zone are 

 widely distributed in alpine or arctic regions of Xorth America, and 

 some of them occur also in similar situations in Europe and Asia. 



EXPLORATIONS AND CERTOX STUDIES ON THE FLORIDA KEYS 

 Dr. Paul Bartsch, curator of marine invertebrates, U. S. National 

 Museum, joined Dr. .Mfred ( i. Mayer, the Director of the Tortugas 

 Marine Biological Laboratory, of the Carnegie Institution, in New 

 "\'ork on December 28. when they sailed south for Kev West to 

 make an examination of the Cerion colonies discussed in ])revious 

 Smithsonian exploration pamphlets. The ])reeding exjicriments 

 presented an entirely new i)hase. in the crossing, on one of the keys, 

 of the native species. Cerion iiiciiiiiini (llinney) with one of the 

 introduced Bahama species, Cerion z'iare^i:;is Bartsch. It was this 

 discovery that made it desirable to start an entirely new set of cxjieri- 

 ments. l^'urthermore, the anatomical differences discovered in the 

 dissections of Cerions also made it dcsiral^le to gain material from ;ill 

 the colonics now existing on the I'^lorida Kevs, in order that these 

 might be subjected to anatomization, to (Utt-nninc if Cei-ioii ineanitin 

 is really one S])ccies, or a complex, shell characters alone bi-ing 

 insufficient to determine this point. It was for this double ri'ason 

 that a return was made to i'"lorida on Ma\- _'. and .m exploration of 

 the keys adjacent to Miami at once undertaken. 



On the ^(1 Capt. 'I'racy anrj Dr. I^artsch started in tlie " D.iruiu." 

 a shallow draught launch of (he Carnegie Instittuioii, fur .in ixplor.i- 

 tion of the shores of the mainl.ind of the lower pt'iiin^nj.t ;ind the 



