290 MINNESOTA BOTANICAL STUDIES. 



7. Cross section of epidermis and cortex of holdfast, x 250. 

 S. Cross section through epidermis and cortex of stipe. X 250. 

 9. Detail of cortex cells of stipe, x 250. 



10. Cross section through pith strand of stipe, x 250. 



11. Longitudinal section through pith strand of stipe, x 250. 



12. Cross section through epidermis of lamina, x 250. 



13. Cross section through cortex and pith strand of lamina, x 250. 



14. Diagram of cross section of leaf showing thickening of margin 

 due to increase of cortex and pith strand, X 30. 



15. Section of cystocarp showing spores inclosed by row of clear 

 cells, x 250. 



16. Oogonium and accessory cells among cortical cells of lamina 

 X 250. 



17. Another oogonium and accessory cell, X 250. 



Plate XLV. 



1. Outline of young thallus of Microcladia coulteri from the base 

 of which project long rhizoid-like cells into the cortex of the host 

 plant, x 170. 



2. Young filament of Callithamnion among cells of host, x 170. 



3. Filament of Callithamnion bearing tetragonidia, x 170. 



4. Young frond of Porphyra epiphytic on parasitic Callithamnion, 

 X 170. 



:;. Chlorochytrium i?zclnsum lying in epidermis of host, x 170. 



6. Endophytic parasite of unknown genus consisting of four cells, 

 X 170. 



7. Same parasite surrounded by epidermal cells, x 17°* 



5. A diagram of cross section of lamina showing relative positions 

 of cystocarp, parasitic Callithamnion and endophyte, x 20. 



