128 FERN GROWING 



In planting the divided portions of a prothallus or prothalli 

 they should always be cut in the same manner, and this is not 

 difficult to accomplish, provided they are not growing thickly 

 together. The upper halves should be kept in one pan, and the 

 lower halves in another, for by this precaution the author has 

 found that no male organs have shown themselves in the 

 former, or female organs in the latter. (Fig. 59, p. 130.) 



One of the experiments to test whether the skipjack could 

 impregnate a prothallus may now be described. Portions of 

 prothalli having only female cells were planted in a pan and 

 protected by an inverted wine-glass ; outside this, other portions 

 having only male organs were then planted ; and the whole were 

 enclosed under a tight-fitting bell-glass. Skipjacks were intro- 

 duced into the outer portion, and a few days afterwards the 

 wine-glass was removed, and the skipjacks allowed to move 

 freely amongst all the prothalli, and several weeks later fronds 

 began to appear. A second pan was planted with prothalli 

 having both male and female organs, though on separate por- 

 tions ; these were planted half-an-inch apart, and kept covered 

 with a bell-glass for three months, but no fronds were formed ; 

 but after the introduction of the skipjacks, it was soon apparent 

 that impregnation had taken place. It is a striking fact 

 that both the male and female organs have remained in a 

 condition to propagate their species after remaining in the 

 prothalloid state for seven and a half years. 



On looking closely into the circumstance of how the spores 

 of four varieties can be made to produce a plant having the 

 characters of all four, it seems that this might be attained by 

 the male organs of three varieties each impregnating a separate 

 cell ; these cells, being on the same prothallus, may by assimila- 

 tion commingle the characters, and a single sperm in each cell 

 might produce the result ; but this would not produce that 

 graduation of characters which has been so frequently shown — we 

 should not raise plants, some having a slight trace, and others a 



