544 Farmer . — On the Structure of a Hybrid Fern. 
Fig. 13. Sporangium from ‘reverted’ frond of the same fern. 
Fig. 14. Leaf of P. aureum (under side). 
Figs. 15, 15 a. Two leaves of P. vulgare , var. elegantissimum. Both show 
‘ reverted ’ pinnae. 
Fig. 16. Normal frond of P. Schneideri (under surface). 
Fig. 17. Partially ‘reverted’ leaf of same (upper surface). 
Fig. 18. Under surface of a similar leaf. Sporangia abundant on ‘reverted’ 
parts. 
Fig. 19. Completely ‘ reverted’ leaf of the same. Sporangia very abundant. 
