184 



MORPHOLOGY 



leaves or pinnae more or less modified, and may be said to take the fol- 

 lowing forms: (i) epaulet type (Crossotheca), in which the microspo- 



423 



FIGS. 423, 424. Microsporangia of Cycadofilicales, epaulet (Crossotheca) type: 

 423, diagram of cross section, showing the limb (a), the sporangia (b) showing their 

 attachment (<), and the " central boss" (c); 424, diagram of horizontal section, showing 

 the two-chambered sporangia; letters as before. After KIDSTON. 



rangia are pendulous from a more or less peltate and stalked lamina 

 (figs. 423, 424); (2) cupule type (Calymmatotheca), in which the micro- 

 sporangia occur in cupule-like structures terminat- 

 ing naked branches (fig. 425); and (3) synangium 

 type, in which the microsporangia occur as synangia 

 upon the abaxial face of fernlike leaves. 



Female gametophyte. The female gametophyte 

 is hardly at all preserved, so far as found, and 

 sections of the seed give no evidence as to its 

 structure. 



Conclusions. The chief features of this most 

 interesting group may be summarized as fellows' ,- 

 It is evidently very closely related to the ferns, 

 the resemblance in external appearance being 

 remarkably close. The vascular anatomy is dis- 

 tinctly of the fern type, but with the additional 

 feature of secondary wood, which is a gymno- 

 sperm feature. The microsporangia are hardly 

 FIG. 425. Micro- c hanged from fern sporangia ; but the megaspo- 



sporangia of Cycado- i u i j 



filicales, cupule (Ca- I *n&& are enormously changed, a well-developed 

 lymmatotheca) type: ovule replacing a sorus or a synangium. It seems 

 Codonotheca; sporangia clear that this, the most ancient 



on the inner surface of 



the cupule valves. P lants > w *s derived from still 

 After SELLAODS. ferns. 



group of 

 more ancient 



