62 PTERIDOSPERMEAE [CH. 



similar body is seen still enclosed by the lower microspore. It 

 is by no means improbable that these are antherozoids : they 

 were presumably ciliate like those of Ginkgo and recent Cycads 

 (fig. 396, M). The microspores are approximately 70 p, in length 

 and the supposed antherozoids have a maximum diameter of 

 45 IJL, the latter being about f the size of the sperms of Microcycas 

 and -J the diameter of those of Zamia. The smaller and more 

 delicate cells near the lower microspore (fig. 408, D) are no doubt 

 fungal cells as Miss Benson suggests. With reference to the 

 difficulty of determining the nature of Miss Benson's supposed 

 gametes it is worth calling attention to some figures given by 

 Zopf 1 of vesicular cells and sporangia of the Phycomycetous 

 genera Rhizophidium and Lagenidium in the pollen of Flowering 

 plants and Pines. It has been suggested by Burlingame 2 that 

 the ' gametes ' may be prothallial cells ; but this is very improbable. 



Lagenostoma ovoides Williamson. 



In the memoir in which the genus was founded Williamson 

 described two species from the Lower Coal Measures of Lancashire, 

 Lagenostoma ovoides and L. physoides 3 . The seeds described under 

 the latter name had previously been assigned by him to another 

 new genus, Physostoma, and named P. elegans*. Lagenostoma 

 physoides was afterwards figured by Butterworth 5 who recognised 

 some new features. For this species Prof. Oliver 6 has adopted 

 Williamson's earlier name, Physostoma elegans. The former 

 species, which has recently received exhaustive treatment by 

 Miss Prankerd 7 , agrees generally in its morphological characters 

 with L. Lomaxi, but differs in the structure of the surface-tissue 

 of the integument and in some anatomical features. Moreover 

 no cupules have been found and there is 'very little trace of a 

 layer of separation' such as occurs in L. Lomaxi. Over the 

 surface of the integument is a layer of prismatic cells, much shorter 

 and less palisade-like than those in L. Lomaxi, and there are none 

 of the pegs which are a constant feature in that species. There 



1 Zopf (92) Pis. i. ii. 2 Burlingame (15). 



3 Williamson (77) B. 4 Williamson (76) p. 160. 



5 Butterworth (97). 6 Oliver (09) p. 74. 

 7 Prankerd (12). 



