A SUMMARY OF BOG THEORIES 313 



as defined at the beginning of this paper. Burns (1, p. 105) 

 quotes Transeau (55), Livingston (33) Dachnowski (15, 16) 

 and Pennington (38) as supporting his view, but the same facts 

 wdth regard to definition of terms must be taken into account. 

 Dachnowski (19, p. 513) speaks of the "xeromorphy" of bog 

 plants. 



The xerophytic characters of the Ericaceae, which include 

 many of the plants most characteristic of the sphagnum bogs 

 of the Puget Sound region and of the coastal region of Alaska 

 (e.g. Ledum, Kalmia, Loiseleuria, and Andromeda), have been 

 described by Solereder (54), H. E. Peterson (39), O. G. Peter- 

 son (40), Boergesen (4) and Breifeld (6). The ecological anat- 

 omy of bog plants has been described by Transeau (58, pp. 17- 

 20). Lists of plants characteristic of bogs have been given 

 by Cowles (9, pp. 35-37), Transeau (55, p. 403), Burns (1, p. 

 106), Dachnowski (15, p. 131; 22, pp. 33-34 and 20, pp. 238- 

 248), Nichols (35, p. 204), Pennington (37, p. 56); Rigg (41, p. 

 314 and 42, p. 181) and others. 



WHY ARE PLANTS CHARACTERISTIC OF SPHAGNUM BOGS 



MAINLY XEROPHYTIC? 



a. They may be glacial rehcts. More or less support for 

 this theory has been found (Dachnowski 18, p. 1) in the general 

 opinions given by Gray (26) and by Hooker (28). So far as 

 the ^vl•iter has been able to find, however, neither of these botan- 

 ists made any direct statement with regard to the theory that 

 bog plants are glacial rehcts. They emphasize the general 

 idea that arctic plants came south as a result of the advance 

 of the ice sheet. Some support for this theory is found in the 

 WTitings of Dachnowski (18, p. 1), Harshberger (29), Transeau 

 (55, pp. 409-420) and Schwendener (50). Nichols (35, pp. 212- 

 216) discusses this view but endorses it only with quaUfications. 

 He quotes (p. 216) a letter from Dr. Charles A. Davis stating 

 that the theory of glacial influence except so far as the ice sheet 

 provided favorable topographic conditions for the growth of 

 bogs is practically untenable. Clements (p. 170) states: "The 

 presence in bog plants of modifications characteristic of xero- 



