Morphologie, Befruchtung, Teratologie, Cytologie. 569 



might be a strongly developed canalcell. Following Strasburger, 

 recent writers have regarded these cells as homologous with the 

 archegonial Initials of the Gymnosperms, each containing a Single 

 nucleus which becomes the oosphere-nucleus. In consequence, Wel- 

 witschia has been looked upon as occupying an intermediate position 

 between Ephedra and Gnetum Gnemon. 



In view of the fact now estublished, that the prothallial tube, 

 probably always, contains more than one nucleus, it can no longer 

 be regarded as the arrested initial of an archegonium. That the 

 number of nuclei present in different tubes varies, and that this 

 variability is not connected with the age of the tubes, are strongly 

 opposed to the view that the prothallial tube is an archegonium 

 in any stage of development. If the nuclei are all potentially sexual, 

 as the characters exhibited in the early stages suggest, the tube is 

 no more equivalent to an archegonium than is the whole of the 

 fertile end of the embryo-sac of Gnetum Gnemon. 



The results of this investigation, while far from being conclu- 

 sive, suggest that the fertile end of the Welwitschia prothallus is a 

 more highly specialised form than that of Gnetum. Gnemon, from 

 which it seems mainly to differ in its partial septation, which may, 

 perhaps, be regarded as mereJy a necessary antecedent to the highly 

 advanced type of siphonogamy to which Welwitschia has attained. 

 But even if further research falls to establish this view, it is clear 

 that Welwitschia can no longer be placed in the enormous gap which 

 seperates Gnetum Gnemon from Ephedra. 



That the embryo-sac should send prolongations into the nucellus 

 towards the micropyle is not unknown. Their occurrence in the 

 young ovule of Gnetum. has been recorded, and they are also descri- 

 bed for certain angiosperms. That such prolongations should con- 

 duct the sexual nuclei to meet the pollen-tube appears, however, to 

 be unique. But as siphonogamy has become universal in the higher 

 plants, its is perhaps remarkable that a similar method of carrying 

 the female nuclei to meet the pollen-tube through the lower part of 

 a thick nucellar cap has not been developed in other cases besides 

 that of Welwitschia. The fact that the nuclei are advanced some 

 distance up the nucellus before poUination occurs, implies that, 

 ceteris paribus, the time which elapses between the germination 

 of the pollen-grain and the fusion of the sexual nuclei is much 

 shorter than would be the case had the pollen-tube to transverse 

 the whole distance from the top of the nucellus to the prothallus. 

 In view of the conditions under which the plant lives this fact cannot 

 be without significance. Jongmans. 



Renner, O., Ueber die weibliche Blüte von Juniperus com- 

 munis. (Flora IIIC. 1907. p. 420—430. 6 Abb.) 



Bei der weiblichen Blüte von Juniperis communis, überhaupt 

 der Sektion Oxycedrus, alternieren die drei Samenanlagen, die sich 

 an ihrer Spitze finden, mit dem letzten Blattwirtel des Blütenspros- 

 ses. Verf. giebt nun eine ausführliche Uebersicht der verschiedenen 

 Erklärungen, welcher in der Literatur zu finden sind. Der Haupt- 

 sache nach kann man diese Auffassungen zu zwei Gruppen vereini- 

 gen. Die eine, zu welcher Kubart gehört, ist der Ansicht, dass die 

 Samenanlagen reduzierte Sporophylle darstellen, die zweite, haupt- 

 sächlich durch Schumann und Strasburger vertretene, meint sie 

 seien echt achsenbUrtige Organe. Nach Verf. Meinung sind von 



