366 
I. W. BAILEY 
A number of interesting cytological problems suggest themselves in 
this connection, (i) Are the large, elongated initials multinucleate or 
hyperchromatic in conformity with the generalizations of Sachs, Stras- 
burger, Winkler, and others? (2) Do the nuclei divide mitotically or 
amitotically? (3) What is the nature of cytokinesis in cells which are 
several hundred times as long as they are wide, and yet divide longitudinally? 
These and similar questions will be considered in the next paper of this 
series. 
Summary 
1. Reconnaissance surveys of the higher plants reveal striking variations 
in the dimensions and volume of the cells of the cambium and secondary 
xylem. 
2. Certain of the size variations are purely somatic, whereas others 
are germinal. 
3. In many plants the dimensions and volume of tracheary cells are 
determined primarily by those of the cambial initials, whereas in others 
they are due largely to changes which occur during the differentiation of 
the xylem. 
4. These fundamental types of size variations, and concomitant fluc- 
tuations in form and structure, are significant in the investigation of various 
cytological, morphological, and physiological problems. 
5. The cambium appears to be an unusually favorable medium for 
the study of problems relating to cell size and body size, the working sphere 
of the nucleus, the nucleo-cytoplasmic relation, and phenomena of cyto- 
kinesis in somatic tissues. 
In conclusion, the writer wishes to express his indebtedness to Doctor 
E. D. Merrill, Director of the Philippine Bureau of Science, for his kindness 
in sending carefully preserved and identified specimens of a number of 
tropical plants. 
LITERATURE CITED 
Boveri, T. 1904. Ergebnisse iiber die Konstitution der chromatischen Substanz des 
Zellkerns. Jena. 
Driesch, H. 1898. Von der Beendigung morphogener Elementarprocesse. Arch. 
Entw.-Mech. 6: 198-227. 
. 1900. Die isolirten Blastomeren des Echinidenkeimes. Arch. Entw.-Mech. 10 : 
361-410. 
Hartig, R., and Weber, R. 1888. Das Holz der Rothbuche in anatomisch-physiologischer, 
chemischer und forstlicher Richtung. Berlin. 
Klinken, J. 19 14. Ueber das gleitende Wachstum der Initialen im Kambium der Koni- 
feren und den Markstrahlverlauf in ihrer sekundaren Rinde. Bibl. Bot. 19: 1-37' 
Levi, G. 1906. Studi sulla grandezza delle cellula. I. Recerche comparative sulla 
grandezza della cellule dei Mammiferi. Arch. Ital. Anat. Embriol. 5: 291-358. 
Mischke, K. 1890. Beobachtungen iiber das Dickenwachsthum der Coniferen. Bot. 
Centralbl. 44: 39-43, 65-71, 97-102, 137-142, 169-175- 
Prichard, R. P., and Bailey, I. W. 19 16. The significance of certain variations in the 
anatomical structure of wood. Forestry Quart. 14: 662-670. 
