AMERICAN 
JOURNAL OF BOTANY 
Vol. VII November, 1920 No. 9 
THE CAMBIUM AND ITS DERIVATIVE TISSUES 
II. SIZE VARIATIONS OF CAMBIAL INITIALS IN 
GYMNOSPERMS AND ANGIOSPERMS 
I. W. Bailey 
Introduction 
Much has been written during the last fifty years concerning the relations 
between cell size, and body size, nuclear size, chromosomal number, and 
chromosomal mass. One group of botanists and zoologists, including such 
classical writers as Sachs (1893), Driesch (1898, 1900), and Boveri (1904), 
maintain that the size of the cells in specific organs or organisms remains 
constant regardless of variations in growth or stature, whereas another 
group hold that cell number rather than cell size is fixed. A second con- 
troversy revolves around the question whether the nucleo-cytoplasmic 
relation is a constant or a self-regulating ratio, and, more recently, whether 
dwarf and giant mutants are produced by changes in the number or in the 
size of chromosomes. 
Many of the discrepancies in the conclusions of these writers appear to 
be due to an intensive study of a particular tissue, organism, or stage in 
ontogeny without reference to what may occur in other tissues, organisms, 
or developmental stages. Levi (1906) has shown that in mammals the 
size variations of epithelial and gland cells — elements which continue to 
divide throughout life — are insignificant, whereas such highly differentiated 
cells as nerve fibers, lens fibers, muscle fibers, and ganglion cells tend to be 
considerably larger in large animals than in small ones. Thus, the necessity 
for extensive preliminary, comparative investigations in selecting material 
for intensive experimental research, and to serve as checks upon excessive 
generalization from limited induction, is well illustrated by the literature 
dealing with body size and cell size. 
In the first investigation of this series^ an attempt was made to deter- 
mine, by means of an extensive reconnaissance survey, what are some of 
the more fundamental types of size variations that occur in the tracheary 
^ Bailey, I. W., and Tupper, W. W. Size variation in tracheary cells: i. A comparison 
between the secondary xylems of vascular cryptogams, gymnosperms and angiosperms. 
Proc. Amer. Acad. Arts and Sci. 54: 149-204. 1918. 
[The Journal for October (7: 305-354) was issued November 5, 1920.] 
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