44 MINNESOTA BOTANICAL STUDIES. 



7. Vertical section through periphery of holdfast, showing direction 

 of cell rows. Also shows meristematic character of cells near edge. 

 Disintegrating cells are shaded. 



8. Cross-section through central part of holdfast. 



9. Cross-section through holdfast nearer to the edge of disc. 



10. Edge of holdfast, in cross-section, showing division of cells in 

 this region. 



n. Diagram to illustrate transverse and vertical dichotomy of the 

 cells in the peripheral part of holdfast. 



12. Diagrammatic view of cross-section of stipe or blade to illustrate 

 protoplasmic communication in epidermal and cortical region. The 

 chromatophores have been left out. Shows increase of intercellular 

 jelly toward pith, crowding cells apart, except at the pits, showing 

 formation of protuberances from adjoining cells. 



13. Pith cells showing protoplasmic contents, nuclei and chromato- 

 phores. Shows end plates apparently permitting protoplasmic com- 

 munication. 



14. Shows lateral pits at anastomosing point of two pith cell rows. 



PLATE X. 

 Anatomical detail. 



15. Growing point with apical cell dividing in two lateral and a basal 

 plane, rapid multiplication of cells in the lateral regions ; less rapid 

 in the axial region. Rapid differentiation into pith in axial region ; less 

 rapid in the wings. Illustrates mode of bifurcation, X 375- 



1 6. Same in diagram. 



PLATE XI. 



Anatomical detail. Development of conceptacle, X. 300. 



17. Beginning of conceptacle. Shows basal cutoffs and disintegrat- 

 ing epidermal cells above them. 



1 8. Same in diagram. 



19. Later stage. Shows collapse of a central epidermal cell, remains 

 of same appear as small cone on basal cutoff. Other epidermal cells 

 are. disintegrating, having however first succeeded in again cutting of 

 a basal cell each, which have grown obliquely into the cavity formed 

 by collapsed cell. 



20. Diagram of same. 



21. Later stage, more epidermal cells affected. Cavity filled with 

 mucilage. 



22. Diagram of same. 



23. Later stage, basal cells disintegrating. Shows division going 

 on in meristematic layer beneath. 



24. Diagram of same. 



