go Campbell. — On the Prothallium and Embryo of 
EXPLANATION OF FIGURES IN PLATES 
III, IV, V, AND VI. 
Illustrating Professor Campbell’s paper on Osmunda. 
PLATE III. 
Fig. i. Fresh spore of Osmunda claytoniana. a , surface view from above; 
b, optical section ; c , a similar spore beginning to germinate, x 350. 
Fig. 2. Microtome-section of a similar spore, fixed with chromic acid and 
stained with haematoxylin. x 650. 
Fig. 3. A germinating spore of the same, a, in optical section ; b , surface 
view ; r, first root-hair ; sp , spore-membrane, x 350. 
Fig. 4. Three very young prothallia of 0 . claytoniana. x 300. In a , the 
nucleus of the end-cell is in process of division ; in b, the apical cell, x, is already 
established ; r, the root-hair. 
Fig. 5. A young prothallium of 0 . claytoniana , in which the first wall in the 
prothallium is at right angles to the wall that cuts off the root-hair, x 300. 
Fig. 6. A young prothallium of O. claytoniana , of the ‘bipolar’ type, sp, 
exospore, x 300. 
Fig. 7. A similar prothallium with the root-hair-lateral, x 300. 
Fig, 8. Prothallium of O. claytoniana , in which no root-hair has been formed, 
x 350- 
Fig. 9. Filamentous prothallium of 0 . claytoniana. x 250. 
Fig. 10. Young prothallium of 0 . claytoniana , showing the apical cell, x. 
x 300. 
Fig. 11. An older prothallium of the same species, x 300. 
Fig. 12. Three very young prothallia of 0 . cinnamomea. The first two walls 
in the prothallium-mother-cell are numbered, x 250. 
Fig. 13. A prothallium of 0 . cinnamomea , the same age as in Fig. 12, but the 
basal cell undivided, x 250. 
Fig. 14. Prothallium of 0 . cinnamomea with apical cell, x. x 250. 
Fig. 15. Young prothallium of 0 . cinnamomea , which has formed a cell-mass 
at once, x 350. 
Fig. 16. Prothallium of 0 . cinnamomea of about the same age as 15, with two 
apical cells, x, x l . x 350. 
Fig. 17. Prothallium of 0 . claytoniana , two weeks old. x 350. 
Fig. 18. Young prothallium of 0 . claytoniana , composed of two parallel cell- 
rows. x 350. 
