408 Palaeontologie. 



Welwitschia appears to afford a clue, for here there arises from 

 each of two primordia, a structure resembling a microsporophyll 

 and bearing three stalked synangia. No opinion is expressed as to 

 whether this sporophyll is a simple branched organ, or a Compound 

 structure formed by the union of three separate microsporophylls. 

 It is however termed a 'unit', and it is shown that the various 

 conditions met with in the three genera, which are shown diagram- 

 matically in a figure, can be derived from that found in Ephedra 

 distachya by the suppression of 1 — 3 of the 'units'. On this view the 

 axial Position of the male organs in Ephedra and Gnetum presents 

 no difficulty, for by the suppression of the female, and their union 

 with one another, they naturally form a median column. 



The male organs do not appear to present any transition to the 

 Angiospermous stamen, but ma}' probably be derived by reduction 

 and fusion from more complicated sporophylls bearing many S3mangia. 



No megasporophyll is believed to be present in any of the three 

 genera. It is pointed out that where reduction has been carried to 

 such extreme limits, it is not surprising that the megasporophyll 

 has totally disappeared, for it played no part in the task of pollen- 

 collection. The female gametophyte is discussed, and the conclusion 

 is expressed that the relationship of the three genera to one another 

 is not so remote as has been supposed. The immediate ancestors of 

 the Gnetales probably had a fairly typical Gymnosperous embryo- 

 sac, which has more or less persisted in the case of Ephedra , but 

 Avhich, in Gnetum and Welwitschia, has undergone considerable 

 reduction with peculiar modifications. 



On this interpretation of the Gnetalean fructifications, it follows 

 that at one time more primitive members of the group existed, 

 possessing typical proanthostrobili, and that the Gnetales are the 

 last survivals of a race, the strobili of which must have presented 

 much variety in form and detail. Consequently the group itself must 

 have once been of some size and complexity, yet at present there 

 is no evidence of such a stock in the fossil State. It is pointed out, 

 however, that this is probably due to the unfortunate position of 

 fossil plants occurring in the Cretaceous and Tertiary rocks. 



The Gnetales are regarded as a race of Gymnosperms, nearly 

 related to the Angiosperms. There are many and varied indications, 

 especially on the view that the Gnetalean strobili may be interpreted 

 as reduced pro-anthostrobili, that both groups have Sprung from 

 common ancestors, and that their lines of development have, in 

 many respects, continüed parallel. These ancestors, the Hemiangio- 

 sperms, as yet a hypothetical race, gave rise to two distinct lines, 

 the primitive Angiosperms (Ranalian plexus) and the primitive 

 Gnetales. Of the latter, three highly evolved genera alone survive 

 at the present day. 



The paper concludes with a table of the relationships of the 

 Gnetales to those groups to which they are here regarded as being 

 most nearlj?- allied and with a füll bibliograph5^ 



Arber (Cambridge). 



Bertrand, C. E., Remarques sur le Taxospermurn angidosiim. 

 (Assoc. fran?. Avanc. Sei. 36^ Sess., Reims. 1907. 11. p. 410—413). 



L'auteur fait connaitre dans ce travail les observations qu'il a 

 faites sur la graine figuree jadis par Ad. Brongniart sous le nom 

 de Sarcotaxiis angulosus^ et il montre qu'aucun caractere essentiel 



