696 CONCLUSION 



two (Fig. 361 G), or by three bract-leaves (Fig. 361 H) : or in Archaeo- 

 calamites and Equisetum the sporangiophores may be borne quite inde- 

 pendently of any bracts. It thus appears that the most usual condition 

 is clearly that where the bract subtends the spore-producing member, 

 whether sporangium or sporangiophore ; but this arrangement is liable to 

 be disturbed by chorisis of either bract or sporangiophore, or by the 

 entire absence of the bract. 



These presumable fissions, which comparison indicates as having 

 occurred in both sterile and fertile parts, deserve attention : it appears 

 that they may affect either class of parts separately or both together. 

 In the simple condition of the Lycopodiales fissions of the appendages 

 are very rare ; but examples have been recorded where two sporangia 

 appear side by side in Lycopodium?- and an occasional case of a bifid 

 protophyll has been observed in the young plant of Lycopodium and 

 of Phylloglossum ; 2 but these characters have never become permanent 

 for any race of Lycopods. In the Equisetales the result of fission is seen 

 frequently in the bracts (Fig. 361 G, H), though not in the sporangiophores 

 of the ancient types ; but in the modern genus Equisetum fission of 

 sporangiophores appears to have been effective. An examination of the 

 very numerous sporangiophores of Equisetum maximum shows frequent 

 cohesion of their stalks, while a comparison of the simpler species, such 

 as E. palustre and of the Calamarians, leaves little doubt that with 

 enlargement fission of the appendages has occurred (Fig. 195). Forking 

 is a marked feature of the leaves in the Sphenophyllales (Fig. 361 i), but 

 not necessarily accompanied by fission of the sporangiophore. In some 

 forms, but not in all, there is, however, such a collocation of the sporangio- 

 phores, in number and position as well as in vascular connection, as would 

 indicate that an increase by fission has occurred to produce them : but 

 this may occur independently of any fission of the bract (Fig. 361 j). In the 

 very complex cone of Cheirostrobus it is highly probable that fission has 

 been effective in both parts, as the vascular connections appear to indicate 

 (Fig. 361 K). Lastly, the branching of leaf and spike, described at length 

 for the Ophioglossaceae (pp. 435-439), can best be understood as the 

 consequence of similar progressive fissions (Fig. 361 L, M, N). It thus 

 appears that fission has probably been a frequent feature in producing 

 the condition of the appendages in the strobili actually observed in the 

 more complex sporangiophoric types, and that such fission may occur 

 independently in either sporophylls or spore-producing members, or 

 coincidently in both. On the other hand, the condition usual in the 

 Lycopods may be regarded as a type which has remained on the simpler 

 basis without fission. 3 



^Annals of Botany, vol. xvii., p. 278. 

 2 Treub, Ann. Jard. Suit., vol. viii., taf. v., fig. 2 A. 



3 By the term "fission," as here used, is to be understood a chorisis which dates 

 from the initiation of the primordium : the fission is . not a branching of a part which is 



