2 6o SCIENCE PROGRESS 



these male organs of Cycadeoideae are merely pinnate, as 

 regards the purely vegetative portion of their fronds, thus 

 resembling the foliage-leaves of this group. Each pinna bears 

 along its axis two rows of compound sporangia or synangia, 

 this character giving them a decided resemblance to the Marat- 

 tiaceous Ferns. These fronds are, thus, if we take their 

 synangial subdivisions also into account, bipinnate. The main 

 rachis has a sterile terminal expansion. They have a circi- 

 nate vernation ; on the whole, therefore, a very Fern-like or 

 Seed-fern-like organisation. They ripen before the female 

 sporophylls, and are completely shed before the latter mature. 

 With the consideration of the male sporophylls we drop the 

 last link of relationship and resemblance of these plants with 

 the Seed-ferns. For in the female sporophylls we have revealed 

 to us structures of a totally different and quite new character. 

 They are borne in great numbers either all over a rounded and 

 fairly flat cushion, representing the much-shortened axis of the 

 cone, or else, in other types, along the lateral surface of an 

 elongated conical axis, from which they project at right angles. 

 Each sporophyll is a long, very slender stalk, of radial symmetry 

 of structure, bearing at its top a female sporangium or seed ; 

 this latter contains an embryo and either a very small amount 

 of endosperm, or none at all. Equally numerous with the 

 seed-bearing sporophylls, and scattered amongst them, are 

 organs which we may assume to be of the nature of sterile 

 sporophylls, which have become modified to subserve the 

 function of a protective pseudo-pericarp ; for each of them is 

 expanded at the top in such a way as to overtop and enclose 

 the seeds of the neighbouring fertile organs, leaving only a 

 narrow orifice for the projection of the micropylar beak. 



Certainly the most plausible view of these seed-bearing 

 pedicels is that they are sporophylls ; but if so, how greatly 

 modified, how enormously reduced from the large, complexedly 

 organised female sporophyll of the Seed-ferns ! Yet this need 

 not surprise us. For it is just this process of reduction in com- 

 plexity and in size which we discover to be a constant concomi- 

 tant of evolution in whatever direction we turn our gaze. The 

 passage, in fact, from the reproductive department, so to speak, 

 of the organisation of the Seed-ferns to that of the Cycadeoideae 

 has been effected as follows : The s-porophylls have been reduced 

 in size and complexity of structure at the same time that they 



