ARCHEGONIA OF FERNS. 361 



prothallium, selected for the examination of the archegonia, some 

 quite young ones, rich in antheridia. If spermatozoids are 

 diffused in the preparation, we see them, so long as the arche- 

 gonia are closed, quietly swimming by them. If, on the other 

 hand, an archegonium has opened, the spermatozoids, from a 

 measurable distance round, take the direction of the mouth of 

 the canal, and are intercepted there by the mucilage. Within 

 this mucilage their movement is slackened, but they retain their 

 original direction ; they enter into the neck -canal, and reach the 

 oosphere, into which they are absorbed. It has been determined 

 that here also there takes place the secretion, from the neck of 

 the archegonium, of a substance which acts as a chemical stimulus 

 to the spermatozoids, and determines the direction of their move- 

 ment. The specific stimulant in this case is malic acid, which 

 to the extent of about 0'3 per cent, is represented in the mass 

 evacuated from the neck of the archegonium. Thus these sper- 

 matozoids can be successfully attracted into capillary tubes, which 

 are fused at one end, and are injected under the air-pump with 

 a fluid which contains O01 to 0*1 per cent, malic acid, combined 

 with any base, in exactly the same way as into the neck of the 

 archegonium. The spermatozoids of Ferns swarm into large 

 hairs exactly as they do into capillary tubes, best of all those 

 of the leaves of Heracleum Sphoiidylium (the Hog- weed, or 

 Cow -parsnip), if these are laid, with their ends cut off, in water 

 containing spermatozoids. For the spermatozoids of the mosses, 

 cane-sugar, as we have seen, is the specific stimulant. It has 

 been experimentally determined that a single sperniatozoid suf- 

 fices for fertilisation ; but usually several penetrate into the 

 archegonium, of which, however, only one finds admittance. 

 The spermatozoids do not take their posterior vesicle with them 

 into the archegonium ; but, so far as they reach it with the vesicle 

 still clinging to them, it is left in the mucilage in front of the 

 opening. Now and again the number of the spermatozoids which 

 arrive is so large that the)* ultimately bore in between one 

 another, and, elongating thread-like, fill up the entire canal of the 

 archegonium, and even still form a tuft before its opening. The 

 neck of the fertilised archegonium contracts rapidly at its lower 

 end, and in from eight to ten hours commences to turn brown. 



If, after completing our studies of the sexual organs, the 

 general material is kept frequently sprayed, in from eight to ten 

 days we can readily see the first stages of development of the 



