October 13, 1911] 



SCIENCE 



469 



ing than the discovery, by the patient and 

 thorough researches of Professor Oliver, of 

 the connection between Lyginodendron and 

 the well-known paleozoic seed, Lageno- 

 stoma. With Dr. Scott as sponsor, this 

 new and startling revelation met with 

 ready acceptance, and, thanks to the inde- 

 fatigable energies of paleobotanists, no 

 fossil fern seemed at one time safe from 

 possible inclusion among the Pterido- 

 spermse. 



The infectious enthusiasm with which 

 the discovery of the seed-bearing habit of 

 the Lyginodendreffi and the Medullosa 

 was greeted carried all before it, and we 

 in England, particularly, have perhaps not 

 looked carefully enough into the founda- 

 tions upon which rested the theory that 

 these groups form the "missing links" 

 between the ferns and eycads. A criticism 

 against the wholesale acceptance of this 

 view has been put forward by Professor 

 Chodat,^ of Geneva, that distinguished and 

 versatile botanist, whom we have on sev- 

 eral occasions had the pleasure of welcom- 

 ing in our midst. Couched throughout in 

 friendly and courteous language, and full 

 of admiration for the work of those who 

 were concerned in the establishment of 

 the group of Cycadofiliees, now termed 

 Pteridospermse, Professor Chodat suggests 

 that English paleobotanists have not suffi- 

 ciently appreciated the work of Bertrand 

 and Corneille* on the fibro-vascular sys- 

 tem of existing ferns, and have not revised, 

 in the light of the researches of these 

 French investigators, the interpretation 

 given to the arrangement of the primary 

 vascular tissues of Lyginodendron. In 



' Chodat, E., ' ' Les Pteropsides des temps paleo- 

 zoiques, " Archives des Sciences physiques et not- 

 urelles, Geneve, Tome XXVI., 1908. 



* Bertrand, C. E., and Corneille, F., ' ' Etude sur 

 quelques eharaeteristiques de la structure des fili- 

 cinees actuelles, " Travaux et memoir es de I'TJni- 

 versite de Lille, 1902. 



Chodat 's opinion the structure of the 

 primary groups of wood found in the stem 

 and in the double leaf-trace of this plant 

 is not directly comparable with the ar- 

 rangement found in the petiole of existing 

 Cycads. In the latter the bulk of the 

 metaxylem is centripetal, while we have in 

 addition a varying amount of small-celled 

 centrifugal wood towards the outside of the 

 protoxylem, and though separated from it 

 by a group of parenchymatous cells, the 

 bundle may be conveniently described as 

 mesarch. In Lyginodendron, and the same 

 applies to Heterangium, the primary 

 bundles of the stem appear at first sight 

 to be mesarch too, but in Chodat 's opinion, 

 if I understand him correctly, the meta- 

 xylem is exclusively centrifugal in its de- 

 velopment, but, widening out and bending 

 inwards again, in form of the Greek letter 

 M, the two extremities of the metaxylem are 

 united on the inside of the protoxylem, 

 forming an arrangement described by Ber- 

 trand and Corneille in the case of several 

 fern petioles under the name of "un diver- 

 geant ferme. " 



Several details of structure, such as the 

 type of pitting of the metaxylem elements 

 and the separation of the protoxylem from 

 the adaxial elements of metaxylem by 

 parenchymatous cells, confirm Chodat in 

 his view that the primary bundles of 

 Lyginodendron are not really mesarch, and 

 that the stem of Lyginodendron is essen- 

 tially Filieinean in nature. Chodat cites 

 other characters, such as the presence of 

 sclerized elements in the pith, and the ab- 

 sence of mucilage ducts, in support of his 

 view of the purely filieinean affinities of 

 the Lyginodendreffi. The presence of sec- 

 ondary thickening in Lyginodendron he 

 regards not as indicative of Cycadian 

 affinity, but merely as another instance of 

 secondary growth in an extinct Crypto- 

 gam, taking up very much the position of 



