EEV. M. J. BERKELEY ON A SUPPOSED HYBRID EERN. 139 



comparison, are aware that this frond is the result of impregnation. 

 One of the first persons to observe the production of little tuber- 

 cles filled with active molecules on the underside of the filmy disks 

 (or proembryos, as they are sometimes called) was Mr. J. Hender- 

 son, for many years gardener to Earl Fitzwilliam, and one of the 

 most talented persons I have ever had the good fortune to reckon in 

 the number of my friends. Other observers perceived that there 

 were two kinds of tubercles, that one of these, the antheridia, or 

 male organs, contained a number of minute ciliated bodies (sper- 

 matozoids), which moved about like Infusoria when in water, and 

 were destined to impregnate the little embryo-cell situated at the 

 base of the female tubercles, called pistillidia or archegonia. As 

 these spermatozoids can move about only where there is sufficient 

 moisture, it is obvious that a proper supply of water is an abso- 

 lute necessity in the act of impregnation. Where the spores of 

 different species of fern chance to germinate on the same limited 

 spot, it is very possible that the spermatozoids of one species 

 may obtain access to the embryo-cell of another, and thus a true 

 hybrid may arise. As, however, the proembryos are for the 

 most part closely pressed to the surface of the soil, and often 

 bound down by little rootlets, they are not situated in very fa- 

 vourable circumstances for impregnation. 



What steps, therefore, should the cultivator take to give him 

 any chance of success in experimenting for the production of hy- 

 brid ferns ? It is first absolutely necessary that he should work 

 with species whose proembryos come to maturity at the same mo- 

 ment. A good pocket-lens, and ordinary accuracy of observation 

 will easily enable him to ascertain this, and if he finds that one 

 species comes to maturity more rapidly than another, it will be 

 necessary for him to sow the spores a few weeks later, as the indi- 

 vidual case may make it requisite. Having the proembryos on 

 which he wishes to experiment in a proper condition, he must 

 have recourse to a little delicate manipulation. That of the male 

 parent will give him little difficulty. He will merely have to lift 

 it up from the soil, and with a camel' s-hair pencil and a small drop 

 of water, wash off a quantity of the spermatozoids, taking care to 

 apply his brush where there is no soil attached to the mem- 

 branous body. He will then very carefully lift up the edge of the 

 proembryo which is to supply the female parent, and touch the 

 minute archegonia with his brush, and in all probability some of 

 the spermatozoids of the strange plant will obtain entrance. It is 

 true that in many cases its own spermatozoids will gain admission ; 



