ASEXUAL GROWTH FROM PROTHALLUS OF PTERfS CRETICA. 271 



eine Sprossenbildung , ungefiilir an dcr Stelle dcs Lagers wo 

 das beblatterte Pfianzchen angelegt wild, entspringen junge 

 Vorkeime von derselben Gestalt, wie die Hauptvorkeime im 

 jungen Zustande, mit dem verschmalerten Ende (dem Spore- 

 nende entsprechend) , an dem Lager festsitzend, spater sich 

 loslosend und wie ein selbstandiger Vorkeim sich verhaltend." 

 From the above paragraph, it woukl be, perhaps, difficult to 

 say whether Wigand had seen anything similar to our case. 

 But, taken in connection with his Tafel 1, fig. 25, where a 

 process in the concavity is clearly seen, it seems probable 

 that he had seen a growth which did not proceed from a 

 fertilized archegonium.^. 



The bearing of the facts already enumerated upon the 

 question of the function of the fern-prothallus is very im- 

 portant. Since the publication by Leszcyc-Suminski, in 

 1848, of his observations concerning the sexuality of ferns, 

 the prothallus has been regarded as an organ intermediary 

 between the spore and the fully -developed plant, growing 

 out of the former, and bearing sexual organs which by mutual 

 co-operation produce the latter. It has been considered im- 

 possible for a spore to produce a fern-plant directly without 

 the intervention of a sexual union.^ But, from the cases we 

 have been considering, it is evident that this process is not 

 absolutely necessary, since we have seen that a young fern 

 can be produced from the spore by a purely vegetative or 

 budding process — a process as clearly un sexual as, for instance, 

 the production of plantlets on the fronds of Asplenium vivi- 

 parum. This fact is an unexpected one for those who con- 

 stantly see unity and simplicity in nature. Although in by 

 far the majority of cases the prothallus does bear archegonia 

 whose embryos develop into ferns, the monstrosity, if so we 

 please to call the present cases, having once been noticed, 

 may of course be expected to occur at any time ; and, now 

 that the attention of botanists has been called to it, it may 

 prove not to be rare. As, in the present instance, certain 



' As far as I am aware, no similar cases are described in any of 

 Hofmeister's writings ; but, on the authority of Dr. Askenasy, of Heidelberg, 

 an example of a similar prothallus was shown by Hofmeister, when pro- 

 fessor at Heidelberg, to the students in his laboratory. At any rate, a fern 

 prothallus containing one or more vessels was seen by him, and probably a 

 scantiness of material prevented a further study of the subject. 



- [Sachs remarks that, like the thalli of HepaticfS, the prothalli of ferns 

 develop adventitious branches from some of their marginal cells, and this 

 takes place especially in Osmunda, where the adventitious shoots detach 

 themselves, and so constitute a means of vegetative propagation. Appa- 

 rently it is only the tliallus that is produced in this way, and not, as in the 

 present case, the asexual generation. — Ed.] 



