i8 



GYMNOSPERMS 



Fig. 12. — Crossolheca hoenighatisi: 

 leaf with both sterile and fertile pin- 

 nae. The sterile leaves were known as 

 Sphenopteris hoenighausi, later found 

 to be the leaf of Lyginopteris; X2. 

 From a sketch made from a photo- 

 graph by KiDSTON. 



of Lyginopteris (fig. 12). Thtir fertile pinnules are more or less pel- 

 tate, each bearing six or rarely seven pendant, bilocular microsporan- 



gia, the whole structure resembling 

 the microsporophyll and sporangia 

 oiAraucaria. The microsporangium 

 is about 3 mm. long and half as wide, 

 with microspores 50-70 microns in 

 diameter. Sections of microspores 

 show tissues of cells, but not so defi- 

 nitely as to prove whether they are 

 prothallial or spermatogenous (figs. 

 13 and 14). 



The microspores, or pollen grains, 

 alighted so close to the female ga- 

 metophyte, perhaps even in contact 

 with the neck cells of the archego- 

 nia, that there could not have been 

 any pollen tubes. The sperms must 

 have been shed much as in Isoetcs, 

 Selagi?iella, and the water ferns. Consequently, there could have 

 been no prolonged interval 

 between pollination and fer- 

 tilization, an interval of 

 months in most of the living 

 Gymnosperms. Engler's 

 term. Si phono gamia, would 

 not be appropriate for these 

 early seed plants. 



Miss Margaret Ben- 

 son''^ (fig. 15) described an 

 interesting section through 

 the nucellus of Lagcno- 

 sloma ovoides, showing pol- 

 len grains in the pollen 

 chamber, two of them with the intine protruding from the spore, 

 reminding one of the protrusion of the male gametophyte in 

 Azolla. She even showed bodies, described as sperms, in the pollen 



Fig. 13 



Fic. 14 



Fig. 13. — Stephanospernium akcuioides: sec- 

 tion of a pollen grain, showing cellular struc- 

 ture. — .After Oliver. •'•'^ 



Fig. 14. — Physostoma elegans: section of a 

 pollen grain, showing internal structure; the 

 (lotted part is the e.xospore, where it has not 

 been ground away in making the section; X480. 

 —After Oliver."' 



