1902-1903.] Report of the Microscopical Section. 61 



one, and in favourable circumstances may reach half an inch 

 in length and at the widest part about a quarter of an inch in 

 breadth. It lies like a scale upon the ground, and from its 

 under side numerous root-hairs arise ; and it is also on this 

 under side that the sexual organs — the antheridia and arche- 

 gonia — are produced. This prothallus is the oophyte or sexual 

 generation of the plant. 



As a general rule, both antheridia and archegonia are pro- 

 duced on the same prothallus ; but in certain cases, especially 

 if its nourishment has been defective, the prothallus may only 

 bear antheridia. The antheridia give rise to the sperma- 

 tozoids or male organs, which are liberated from their mother- 

 cells by the bursting of the latter under the influence of water. 

 While the antheridia have been maturing so also have the 

 archegonia, in the venter of each of which is formed an ovum. 

 When an archegonium is ripe, some of the cells forming 

 its neck become disorganised, and their protoplasm is con- 

 verted into mucilage, which swells up, and thus forces open 

 the passage in the neck, and also exudes and forms a viscid 

 drop at the mouth. If, then, water be on the ground, and 

 any of the liberated spermatozoids are brought under the 

 influence of the viscid drop at the mouth of the archegonium, 

 one of them is caught in it, and wriggles down the neck till it 

 reaches the ovum, which it fertilises. The fertilised ovum then 

 gives rise to the embryo of an independent young fern plant. 



In addition to this mode of reproduction, some ferns repro- 

 duce themselves vegetatively by means of small buds or young 

 plants on the fronds, such, for instance, as the As'plenium 

 Fahianum and others of that genus. 



The last type studied was one of the Equisetacese or Horse- 

 tails — the Uquisetum arvense. This genus is also homosporous, 

 and here also there is alternation of generations, which in many 

 respects closely resembles that of the ferns ; but the want of 

 space prevents any detailed description. 



The book followed was D. H. Scott's ' Structural Botany,' 

 Part II., " Flowerless Plants." 



During the session Mr G-. T. West, of the Eoyal Botanic 

 Garden, gave several interesting demonstrations on the proper 

 method of obtaining a critical illumination of objects under 

 the microscope. 



