Ll] CYCADOCARPIDIXTM 451 



by these seed-bearing organs favours a Cycade^n alliance : on the 

 other hand he has satisfied himself that some Podozamites specimens 

 are shoots with spiral Unear leaves hke those of Agathis. It is in 

 many cases very difficult to say whether the axis of a Podozamites 

 bears the leaves in two ranks or spirally. Nathorst speaks of 

 some examples in which the leaves are not spiral and suggests the 

 existence of two kinds of branch some with spiral and some with 

 two-ranked leaves as in certain Conifers. But if this is the case 

 one can hardly imagine that the two-ranked arrangement is not 

 due to the twisting of the leaves of shoots with spirally disposed 

 foliage. In a recent contribution to the systematic position of 

 Podozamites Schuster^ speaks of Cycadocarpidium Erdmanni as 

 differing from C. Swabii in the presence of two 'rudimentary 

 leaflets' (the triangular lamina shown in fig. 812, B) which in the 

 latter species are represented only by two small swellings at the 

 upper ends of the seeds: he regards C. Erdmanni as the more 

 primitive type. The lamina is homologised with the cover-scale 

 or bract of the double cone-scale of the Abietineae; he compares 

 the two leaflets of C. Erdmanni and the swellings in C. Swabii with 

 abnormal seminiferous scales of an Abietineous cone. Schuster's 

 view is that Podozamites distans is a primitive Conifer evolved 

 from the base of a Cycadofilicinean line which gave rise to the 

 Ginkgoales, a supposition based on a very slender foundation. 

 Nathorst regards Podozamites as an intermediate type related both 

 to Cycads and Conifers; he does not, however, overlook the fact 

 that the sporophylls of Cycadocarpidium may be compared with 

 those of some Conifers even though their resemblance to Cycadean 

 sporophylls would seem to be closer. Additional data are needed 

 before we can settle the position of Podozamites, but such informa- 

 tion as we have may be said to point to the conclusion that it is 

 nearer to the Conifers or the Ginkgoales than to any other group of 

 Gymnosperms. Nathorst calls attention to a similarity between 

 Yokoyama's Ginhgodium Nathorsti^ and separate leaves of Podo- 

 zamites ; a similar comparison may be made between the latter genus 

 and Eretmophyllum, a genus instituted by Thomas^ and referred 

 to the Ginkgoales (cf. figs. 658, 659, pp. 59, 62). There is indeed some 

 resemblance between Cycadocarpidiwn sporophylls and abnormal 

 ^ Schuster (114). = Yokoyama (89) B. Pis. viii., ix. « Thomas (13). 



29—2 



