THE CAMBIUM AND ITS DERIVATIVE TISSUES 
29), but when it is oblique the division figure tends to assume a diagonal 
position (figs. 8, 11, 12, 13). In ray initials and in longitudinally dividing 
fusiform initials of Pinus Strobus, the chromosomes tend to be twisted and 
crowded together in the nuclear plate (figs. 4, 15), but in wide,^ pseudo- 
transversely dividing fusiform initials, the nuclear plate may be more 
extensive and the chromosomes so arranged that they are nearly all visible 
in a single focal plane (figs. 8, 12). Furthermore, the chromosomes in 
adjoining cells may vary considerably in shape, in certain figures resembling 
hooks (fig. 12), and in others V's or U's of varying widths (figs. 7, 8, 15). 
The shape of the karyokinetic figures, particularly during the prophase, is 
profoundly affected by the shape of the "resting" nuclei. Thus, the 
spirems formed in the stem at the beginning of the growing season, when the 
nuclei are much elongated (figs. 10, 11, 41), may be entirely unlike those 
which are formed subsequently from shorter and wider nuclei (figs. 1,6). 
NucLEO-CYTOPLASMic RELATION (continued) 
In order to determine whether large meristematic cells are hyperchro- 
matic, I have devoted considerable attention to a study of the number and 
size of the chromosomes in the cambium of Pinus Strobus L. Sections were 
secured showing adjacent meristematic cells of various dimensions and 
volumes in equivalent stages of karyokinesis. The large, fusiform initials 
do not contain the tetraploid or polyploid number of chromosomes. All 
cells regardless of their size have approximately the diploid number (24).^ 
It is evident, accordingly, that the variations in the size of the nuclei and 
cambial initials of P. Strobus are not dependent upon variations in the 
number of chromosomes. Are they correlated with fluctuations in the 
size of chromosomes? 
Erdmann (1908) concluded from her investigations upon sea urchins 
that chromosomal mass, rather than chromosonal number, is the size- 
determining factor of cells. Conklin (1912) considered that in comparable 
cells of Crepidula large protoplasts have larger nuclei and chromosomes 
than small protoplasts. Hegner (1920) reaches similar conclusions in a 
recent paper upon Arcella. If there is a close correlation between chromo- 
somal mass and volume of cytoplasm, the adjacent cells of the cambium 
vary so greatly in volume that there should be a striking contrast in the 
size of their chromosomes. This does not appear to be the case, however, 
in any of the material that I have studied. The chromosomes in a small 
ray initial having a capacity of 3,000-10,000 cubic microns may be fully 
as long and thick as those which occur in an adjoining fusiform initial with 
a volume of 1,000,000-5,000,000 cubic microns. Figures 4, 5, 17, 18, 12, 13, 
28, and 29 are from fusiform initials having capacities of 800,000-1,200,000 
cubic microns, and figures 15, 16, 30, and 31 from ray initials with volumes 
2 Tangential dimension. 
3 Miss Ferguson (1904) has shown that the haploid number is 12. 
