FERN CONFERENCE. 



497 



As a key to the whole may be taken the case of the sporan- 

 gium, and it is to be noted that the facts of development were 

 first worked out in the sporangium, and upon them were based 

 the distinction of Eusporangiate and Leptosporangiate Ferns. 

 Taking first those of simpler construction, the sporangium is 

 there seen to originate from a single superficial cell, which pro- 

 jects as a single cell beyond the general surface of the leaf which 

 bears it, before the segmentation begins. The divisions of this 

 cell are for the most part definite and regular, and the result is 

 the development of a stalked sporangium, of relatively small 

 size, with a wall consisting, when mature, of a single layer of 

 cells, which encloses the mass of spores ; to this more simple 

 type belong the sporangia of t\\QHyvienopliyllaccce,Polypodiacc(Zy 

 and CyatheacecB, which are accordingly styled collectively, to- 

 gether with certain other minor families, the Leptosporangiate 

 Ferns. At the other end of the series are to be placed those 

 Ferns which have a more bulky type of sporangia ; here they 

 originate as an outgrowth of a mass of cells, not referable in 

 origin directly to a single parent cell. The segmentation in these 

 is not so definite or strictly regular, and the individual sporan- 

 gium when mature is not stalked, but is inserted by a broad base 

 either directly upon the frond or upon a joint outgrowth at the 

 base of the whole sorus. The sporangia themselves are often 

 laterally confluent, so as to form large masses, or they may be 

 deeply sunk in the tissue of the frond. To this type belong the 

 Marattiacece and Opihioglossacecs, and they are styled the Eu- 

 sporangiate Ferns. 



Between these extremes are found, as intermediate types, the 

 Schizceacece, of which the affinities appear to be rather to the 

 Lcptosporangiatce, and the OsmundacecE, which constitute a well- 

 marked connecting link between these and the Eusporangiatce, 



It has been found, as the result of a comparison of the other 

 parts of Ferns of the above families— viz. stem, root, leaf, and 

 wings of leaf — that, as regards regularity of segmentation and 

 relative complexity of structure, there is a remarkable paral- 

 lelism with the characters of the sporangium, so that the 

 sporangium may be taken as a general index of the nature of the 

 other meristems ; where the segmentation of the sporangium is 

 precise and regular, as is the Leptosporangiate, the same is 

 the case with several apical meristems, while in the Eusporan- 



