Febeuaey 4, 



!•] 



SCIENCE. 



163 



the following points may be regarded as 

 settled : 



1. Phylloglosmm drummondii is the simplest 

 known living Pteridophyte. 



2. The fertile spike of Ophioglossum is 

 derived by sterilization in transverse planes 

 of a bilocular Tmesipteris-like sporangium. 



3. Tmesipteris tannensis is, of known forms, 

 the club moss nearest to the Filicinte. 



4. The sporangia-bearing leaves of Marat- 

 tiaceffi and Leptosporangiate ferns homolo- 

 gize with the fertile spikes alone of Ophio- 

 glossum leaves. 



5. In the sense in which sporophylls occur 

 in Lycopodinse they also occur in ferns 

 among the Ophioglossacese, but in Marat- 

 tiacete onlj^ the stipules remain to represent 

 the old sporophyll lamina of archetypal 

 ferns. In Leptosporangiate ferns even the 

 stipular vestige has disappeared. 



6. The Isoetaceas, Salviniacese and Mar- 

 sileacete are terminal groups. 



7. Either seed-producing plants are of 

 polyphyletic origin or the multiciliate type 

 of spermatozoid has been developed in more 

 than one branch of archegoniate plants. 



Concerning the latter point it is proper 

 to observe that most students of phylogeny 

 have looked for the archetype of the 

 ConiferfE in the vicinity of Selaginella. It 

 will be noted that all genera of seed-pro- 

 ducing plants known to produce spermato- 

 zoids do not produce biciliate, but multi- 

 ciliate, spermatozoids. The embryogeny, 

 however, of Lycopodinte, notably of 

 Selaginella, is much more similar to that 

 of seed-producing plants than is the em- 

 bryogeny of such ferns as IscEtes. With 

 Isoetes and the Marattiacese the Cycads, 

 however, show some striking points of 

 similarity, and it may be that this group of 

 seed-plants is allied rather with Filicinse 

 than with Lycopodinse. If it be accepted 

 that the prevalent pinnation of fern leaves 

 is really of very profound significance and 

 indicates the presence among their ances- 



tral types of a Tmesipteris-like form with 

 bilocular bilateral sporangium, capable of 

 development into the fertile spike of 

 Ophioglossum, it may also be held as 

 probable that the pinnation of carpellary 

 leaves of Cycas has a similar profound sig- 

 nificance. On the other hand, the strobi- 

 loid features of the Zamise may also be 

 fundamental and a Selaginella-like ances- 

 tor may, therefore, be proposed. In this 

 case the multiciliate sperm of Gymno- 

 spermse would be held to have an independ- 

 ent origin as compared with the multi- 

 ciliate sperm of Filicinse and Equisetinse. 

 Of Equisetum, indeed, the archetype 

 among living club-mosses would seem to 

 be most closely reproduced in Psilotum 

 with its radially trilocular synangia, and 

 the difiPerence between radia and bilateral 

 synangia may be as important as indicated 

 by Celakowski.* According to this student 

 of phylogeny the radial type of synangium 

 is the most ancient and is perpetuated in 

 Gymnosperms as well as in Equisetinse. 

 There are, however, three types of synangia 

 derived by sterilization of simple Lycopo- 

 dium-like sporangia. These are as fol- 

 lows : 



1. The radial type. Exemplified in Psilo- 

 tum, Equisetum, Taxus. 



2. The bilateral type. Exemplified in 

 Tmesipteris and leading to the fertile spike 

 of Ophioglossum and to the ' sporangiophyll' 

 of Marattiacese and Leptosporangiate ferns 

 and possibly to the carpels and stamens of 

 Cycas. 



3. The reticular type. Exemplified in 

 Isoetes. 



In Cycadacese the sporangial type is, from 

 the pinnation of carpels, originally not 

 trabecular, but bilateral, indicating either a 

 Tmesipteris-like ancestor or an independent 

 bilateral modification of the Selaginella 



* Celakowski, L. J. Nachtrag zu meiner Schrift 

 iiber die Gymnospermen. Engl. Bot. Jhrh. 24:202- 

 231. 17 Ag. 1897. 



