phylogenetic series of micro-sporangiate structures be- 
ginning with the typical 4 sterotheca, then through As- 
terotheca truncata to Crossotheca pinnatifida to the typi- 
‘al Crossotheca to the Whittleseyineae. 
It is not clear, however, whether this is only an im- 
plied transition from a typical fern synangium through 
pendulous encapsulated sporangia to the typical radial 
structure characteristic of the Whittleseyineae,or whether 
it is a genetically related series. 
Thus we come to a brief consideration of the two 
genera under discussion: Codonotheca and Crossotheca. 
Codonotheca is known to be a pteridosperm, its ‘‘pol- 
len’’ (=microspores) are typically cyecadean, and it be- 
longs clearly to the W hittleseyineae. 
Crossotheca is probably pteridospermous, but there 
remains the possibility that at least some of its species 
are filicinean. In Crossotheca sagittata, we may be deal- 
ing with a fern whose spores are typically pteropsid and 
are apparently unicellular. 
The difference in spore structure may not be serious, 
for Crossotheca is attributed to the Lyginopterideae, the 
most primitive group of pteridosperms, while Codono- 
theca belongs to the later-derived medullosans. 
A careful investigation into the phylogeny and rela- 
tionships of the seed-ferns reveals at once the scarcity 
of precise data. The order Medullosae is characterized 
by large ellipsoidal pollen borne in elongate, tubular 
sporangia, which may be fused into a seed-like synan- 
gium. On the other hand, from a survey of the available 
data and materials, it is not possible to circumscribe the 
limits of the Lyginopterideae, nor even to recognize with 
certainty the nature of their microsporangia. Crosso- 
theca, although probably referable to the lyginopterids, 
may yet prove to be filicinean. 
