192 LYCOPODIALES [CH. 



The general generic name Triletes, originally used by 

 Reinsch\ is a convenient term by which to designate Pteri- 

 dophytic spores which cannot be referred to definite types. 



It is usual to find more than four megaspores in each mega- 

 sporangium in Palaeozoic and not infrequently, as we have seen, 

 in Mesozoic lycopodiaceous strobili, but in some Palaeozoic cones, 

 e.g. Boihrostrobus (fig. 216) and Lepidostrobus foliaceus", a single 

 tetrad only appears to have reached maturity. 



The occurrence of long simple or branched and sometimes 

 capitate hairs is a common feature of Carboniferous megaspores 

 (fig. 191, E, F, I). It is possible that these appendages served 

 to catch the microspores, thus facilitating fertilisation. A 

 peculiar form of megaspore has been described by Mrs Scott ^ 

 and assigned by her to Lepidostrobus foliaceus, the mega- 

 sporangium of which apparently contained only four spores. As 

 shown in fig. 191, G, a large bladder-like appendage characterised 

 by radiating veins is attached to the thick spore-coat ; it is 

 suggested that this excrescence may be compared with the 

 " swimming " apparatus of the recent water-fern Azolla. The 

 epithet swimming which it is customary to apply to the 

 appendages of Azolla megaspores would seem to be inappro- 

 priate if Campbell* is correct in stating that spores of Azolla 

 are incapable of floating. 



B. Spencerites. 



Spencerites insignis (Williamson). Fig. 192. 



1878. Lepidostrobus sp., Williamson, Phil. Trans. E. Soc, p. 340, 



PI. XXII. 



1880. Lepidostrobus insignis, Williamson, Phil. Trans. E. See, p. 502, 



PI. XV. figs. 8—12. 

 1889. Lepidodendron Spenceri, Williamson, Phil. Trans. E. Soc, 



p. 199, PI. VII. figs. 20—22; PI. vill. fig. 19. 

 1897. Spencerites insignis, Scott, Phil. Trans, p. 83, Pis. xii— xv. 



Another type of lycopodiaceous strobilus, differing suffici- 

 ently from Lepidostrobus to deserve a special generic designation, 



1 Beinsch (81) A. '^ Maslen (99) p. 373 ; Scott, B. (06) p. 117. 



3 Scott, E. (06). -" CampbeU (05) p. 414. 



