274 ^ CENTURY OF PROGRESS IN THE NATURAL SCIENCES 



1935), Kadula (Castle, 1950), Scapania (K. Mliller, 1905; Buch, 1928), Taxile- 

 jeunea (Eifrig, 1937), Sphagnum (AVarnstorf, 1911; Andrews, 1913), Anacolia 

 (Flowers, 1952), Bryum (Podpera, 1942-1951), Calliergon (AVynne, 1945). Cy- 

 clodictyon (Demaret and Potier de la Varde, 1951), Daltonia (Bartram, 1931a), 

 Dawsonia (Burges, 1949), Drepanocladus (Wynne, 1944a, 1944b; Tnomikoski, 

 1949), the Fontinalaceae (Cardot, 1892), Haplocladium (Theriot, 1930; Rei- 

 mers, 1937), Orthodontium (Meijer, 1951), Orthotriclmm (Piccioli, 1932), Pilo- 

 sium and Stereophyllum (Grout, 1945), Plagiothecium (Jedlicka, 1948), Pottia 

 (Warnstorf, 1916), Ulota (Malta, 1933), and Zygodon (Malta, 1926). 



Bryogeography 



Just as the line between monographic and floristic studies is not always 

 easy to define, so we also find complete intergrading between floristic and bryo- 

 geographic investigations. Naturally, a knowledge of the species concerned 

 forms a major basis for the derivation of any general principles of geographic 

 distribution. Herzog (1926; in Verdoorn, 1932) produced for the first time a 

 clear-cut survey of the general features of the distribution of bryophytes 

 throughout the world. Irmscher (1929) contributed some original ideas con- 

 cerning the significance of present distributions of mosses on the different con- 

 tinents, in the light of the Wegenerian theory of continental drift. Domin (1923) 

 made a major contribution to our knowledge of the world distribution patterns 

 of Ilepaticae. Du Rietz (1940) used bryological materials rather extensively in 

 his study of the problems of bipolar plant distribution. One of the most detailed 

 and helpful works on bryogeography yet to appear is that of Amann (1928), 

 ostensibly covering Switzerland, but really of wide application to most of Europe 

 and much of the rest of the world, with especial reference to the effect of hal^itat 

 and climate on distribution. Although truly enormous, the literature on local 

 and regional studies of bryophytes and their distribution in Europe becomes rea- 

 sonably accessible through several modern publications (cf. ]\Ionkemeyer, 1927; 

 Moller, 1911-1936; Blaringham, 1944; Allorge, 1947; K. Mliller, 1951; and in 

 the pages of Revue Bryologique) . Precise studies on the distribution of bryo- 

 phytes in North America, and of the various factors affecting their distribution, 

 are distressingly few. Attention has been called to special problems of disjunct 

 distribution by Steere (1938), Schornherst (1943), and Sharp (1944), and the 

 erratic distribution of a few species has been related to the maximum extent 

 of Pleistocene glaciation (Steere, 1937; Wynne, 1944a, p. 647). Fulford (1951) 

 has provided a stimulating analysis of the distribution patterns of Hepaticae 

 in South America. In spite of long interest in the geographical distribution of 

 bryophytes and an extensive literature on regional bryophyte floras we have 

 identified only the most generalized types of geograpliic elements over much 

 of the world, and the known distribution of most species of tropical bryophytes 

 reflects, upon careful analysis, only the distribution of botanical collectors. 



Ecology 



Our knowledge of the ecology of bryophytes progressed greatly during the 

 past century, altliough even the earliest bryologists were impressed by the clear- 

 cut correlations between bryophytes and their habitats, and especially by the 



