1902] CURRENT LITERATURE 317 



■J 



L 



North America is subdivided into three provinces: Pacific conifer^ Rocky 

 mountain, southwestern arid or semi-arid. All of these areas are further sub- 

 divided and characteristic formations and species are given in some detail. 

 Occasionally there are errors to be found in the alignment of species, as might 

 be expected in a paper which is largely a compilation from the works of 

 Sargent, Brendel, Mohr, Kurtz, Pound and Clements, and others. However, 

 the broad outlines of the work are remarkably true to the facts. It is par- 

 ticularly interesting to see Atlantic and Pacific America separated into 

 primary divisions, recognizing that the great cleavage lines m the United 

 States run north and south. Ecologists have always known that the plant 

 formations of this country had such an orientation, but many students of 

 floristics during the last decade have attempted to make their great cleavage 

 lines run east and west. We may hardly regard the question as settled, 

 but rather opened up for further study. The details in Engler's paper are 

 remarkably true in most instances; indeed one is obliged to confess that it is 

 the best floristic presentation of the vegetation of this country which has yet 

 appeared. Though designed to indicate the plan of a botanical garden in 

 Germany, it is nevertheless so important a contribution to American phyto- 

 geography as to be a necessary work of reference. — H. C. Cowles. 



R. H. Yapp" has recently treated of the anatomy^ biology, and systematic 

 position of Polyodium {Lecanopieris) carnosiun and Polypodiu??i sinuosum. 

 As to systematic position, he concludes that while that of P, carnosum has 

 been a debatable one, both of the forms should be regarded as closely allied 

 species, both from external features and internal structure. Both are Malayan 

 epiphytes. P, carnosum grows only in the higher branches of trees and 

 usually on fairly high mountains, where it forms thick encrusting masses often 

 several feet in length ; while P, sinuostim, whose creeping rhizomes not form- 

 ing such thick masses as those of P, carnosum are frequently seen quite near 

 the ground, and usually on the trunk itself or on the main branches of its 

 host, is often found almost at sea level. The distribution oi P, simiosKm is 

 more extended than that of P, carnosum. The thick fleshy rhizomes of these 

 epiphytes are tunneled by a system of galleries similar to those of Myrmecodta 

 and Hydnophytum^ and like them invariably inhabited by ants. The origm 

 of the galleries is similar in the two species. About 1-2™" from the growing 

 point and after the differentiation of procambium and protoderm, the paren- 

 chymatous cells in certain definite areas undergo a more rapid increase in 

 size than those of the remaining ground tissue, the difference in size becom- 

 ing more marked farther back from the apex. These zones of tissue, whose 

 cells have increased so remarkably in size with little or no division, are sur- 



" Two Malayan myrmecophilous ferns, Polypodium {Lecanopteris) carnosum 

 (Blume), and Polypodium sinuosum Wall. Ann. Botany 16:185-231. pis. 10-/3. 

 1902. 



i 



