115 



Description of Plates 295, 296. 



Figures I-18 are stages in PUris; figures 19-21 are Adiantum; all figures are 

 drawn with a Zeiss Camera lucida. 



Fig. I. Early sporocytes in the resting stage subsequent to the last division of 

 the archesporial cells. X 1800. 



Fig. 2. Primary sporocyte after growth. Chromatin arranged in a delicate, 

 single, moniliform spireme, nucleolus persistent, X 1800. 



Fig. 3. Primary sporocyte with thickened and concentrated spireme. The end 

 (x) is double. X 1800. 



Fig. 4. Primary sporocyte showing different stages in tetrad formation. C-ring 

 forms. X 1800. 



Fig. 5. Primary sporocyte; portion of nucleus showing stages in tetrad formation. 

 A-double spireme segment ; C-ring forms ; X-divergent forms. X 2300. 



Fig. 6. Various types of tetrad formation; A, B, C, F, G, H, K, L, show the 

 " cross type," D and E the " rod type," I and J the " ring type." X S^oo. 



Fig. 7. Primary sporocyte with finished tetrads. X 1800. 



Fig. 8. Primary sporocyte showing spindle fibres, loss of nuclear membrane, and 

 distribution of the tetrads. X 2300. 



Fig. 9. Primary sporocyte section showing fewer tetrads and the arrangement on 

 the spindle fibres. X 2300. 



Fig. 10. Primary sporocyte, a prophase showing concentration of the tetrads into 

 the nuclear plate. X 2300. 



Fig. II. Primary sporocyte; metaphase showing completed spindle. C-centro- 

 some. X 2300. 



Fig. 12. Primary sporocyte, anaphase showing division of tetrads into dyads. 

 D-dyads. C-centrosome. > 1800. 



Fig. 13. Secondary sporocyte ; metaphase showing arrangement of elongate dyads 

 in the nuclear plate. C-centrosome. X 1800. 



Fig. 14. Late anaphase of the division of the secondary sporocyte showing the four 

 nuclei free in the cell, with connecting spindle fibres. X 2300. 



Fig. 15. Early spores. The cell plates have formed; remnants of the spindle 

 fibres can still be seen. X 1800. 



Fig. 16. Young spore. Nucleoli have reappeared. X '800. 



Fig. 17. Primary archesporium ; a few of the chromosomes during the early stage 

 of division. They are distinctly double. X 2300. 



Fig. 18. Somatic cell from a young fern plant, in division. X 2300. 



Fig. 19. Primary sporocyte {Adiantum) showing formation of tetrads. C-ring 

 form. A-cross form. X 2300. 



Fig. 20. Primary sporocyte showing division of tetrads into the nuclear plate. 

 C-ring forms. X 2300. 



Fig. 21. Primary sporocyte showing division of the tetrads to form dyads. (D). 

 X 2300. 



