STEERE: BRYOLOGY 277 



of bryophytes seems to be that of Garjeanne (in Yerdoorn, 1932). In spite of 

 its simplicity of structure and behavior, in comparison with higher forms, the 

 bryophyte plant resembles the vascular plant very closely in its physiological 

 processes. Since the publication of Garjeanne's excellent review, important 

 physiological studies have been made on bryophytes, of which examples are 

 those of Bowen (1933), Miigdefrau and Wutz (1951), Roberts and Haring 

 (1938), and Buch (1947b) on water relations; of Biebl (1947) on the effect of 

 trace elements; of Meyer and Ford (1943) on the effect of hydrogen-ion concen- 

 tration; of Voth (1943) and Fulford, Carroll and Cobbe (1947) on the responses 

 to variations in the nutrient solutions; of Fulford and Kersten (1947) on re- 

 action to X rays; of Stafelt (1937) on the gaseous exchange of bryophytes; of 

 Walsh (1947) on geotropism and phototropism in the sporophyte of Splachnum; 

 of Hagerup (1935) and Meusel (1935) on growth; of Patterson (1946) on os- 

 motic pressure; and of Meyer (1941) on spore longevity. Many of the researches 

 on the autoeeology of bryophytes are essentially physiological in their approach 

 and in their results, as for example the work of Dombrowski (1933) on spore 

 distribution, the very detailed study of H omalothecium sericeum with relation 

 to its environment by Romose (1940), and the researches on drought resistance 

 by Patterson (1943). 



Cytology 

 Since the tissues of bryophytes are relatively uncomplicated, consisting in 

 many structures of a single layer of cells, they furnish favorable material for 

 cytological observations. The behavior of the cytoplasm and of the cell as a 

 whole in bryophytes has received considerable attention, and the researches on 

 these broader aspects of the cytology of bryophytes has been the subject of an 

 excellent review by Motte (in Verdoorn, 1932). Some observations were made 

 on the behavior of chromosomes in bryophytes well over fifty years ago, and 

 Allen discovered the first sex chromosomes known in plants in the hepatic, 

 Sphaerocarpus, more than thirty-five years ago. However, the most compre- 

 hensive work on the cytology of bryophytes dates from the past twenty-five 

 years, with steadily gained momentum through the years, so that a large body 

 of valuable information has accumulated. Several excellent reviews of cytologi- 

 cal investigations of bryophytes have appeared, by Hofer (in Verdoorn, 1932), 

 by Dopp (1937), by Sinoir (1952), and, for hepatics only, by K. Miiller (1951). 

 Cytotaxonomic investigations of bryologieal problems have begun only very re- 

 cently, and already indicate that this approach will prove as helpful in under- 

 standing the relationships of bryophytes as it has in Crepis, for example. Haupt 

 (1933), Heitz (1942), Lowry (1948), and Vaarama (1950) pioneered the field 

 of cytotaxonomy of bryophytes. Jachimsky (1935) investigated the relationship 

 between sex chromosomes and heterochromatin, with results of wide application 

 elsewhere. So far, bryophytes have received relatively little attention as mate- 

 rial for experimental cytology, in spite of such obvious advantages as their 

 transparent tissues and ease of culture. Wolcott (1941) and Heitz (1945) have 

 investigated the effects of colchicine on nuclear behavior in hepatics and mosses. 



Genetics 

 Technical difficulties of various kinds and the inherent complexity of two 

 alternating generations in bryophytes have tended to restrict genetical research 



