1 84 
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- 
FlGS. 423, 424. Microsporangia of Cycadofilicales, epaulet (Crossotheca) type: 
423, diagram of cross section, showing the limb (a), the sporangia (b) showing their 
attachment (d), 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 follows : 
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 
changed from fern sporangia ; but the megaspo- 
rangia are enormously changed, a well-developed 
ovule replacing a sorus or a synangium. It seems 
clear that this, the most ancient group of seed 
plants, was derived from still more ancient 
ferns. 
FIG. 425. Micro- 
sporangia of Cycado- 
filicales, cupule (Ca- 
lymmatolheca) type; 
Codonotheca ; sporangia 
on the inner surface of 
the cupule valves. 
After SEILAJLDS. 
