I. W. BAILEY 533 



EXPLANATION OF PLATE 1. 



Fig. 1. Scale drawing, showing the relative sizes of ray initials and long 

 initials in the cambium of a 60 year old stem of Pinus strobus L. X 100. 



Fig. 2. Scale drawing, showing the relative sizes of ray initials and large 

 initials in the cambium of a year old stem of Pinus strobus. X 100. 



Fig. 3. Nucleus from large initial shown in Fig. 1. X 1,000. 



Fig. 4. Nucleus from large initial shown in Fig. 2. X 1,000. 



Fig. 5. Nucleus from ray initial shown in Fig. 1. X 1,000. 



Fig. 6. Nucleus from ray initial shown in Fig. 2. X 1,000. 



Fig. 7. Karyokinetic figure in longitudinally dividing cambial initial of Pinus 

 strobus. X 3,000. 



Figs. 8, 9, and 10. Early stages in the formation of kinoplasmasomes and cell 

 plate; (n) daughter nuclei, (k) kinoplasmasomes. X 3,000. 



Fig. 11. Radial longitudinal extension of cambial initial, showing later stage 

 in the formation of the cell plate. X 100. 



Fig. 12. The same. Tangential longitudinal extension. X 100. 



