72 PROCEEDINGS OP THE AMERICAN ACADEMY 



Fourthly, the order of evolution is different in the two cases. In 11, 

 the leaf arose first, as we saw, and was tolerably well developed before 

 a root and afterwards a stem-bud made their appearance. In 14 the 

 root anticipates by far both the leaf and stem-bud in its development ; 

 and, in fcict, the root and stem are not produced from the leaf-stalk, 

 but (and this fact is not to be learned from the figure, but from the 

 accompanying description in Sachs) by the subdivision of a single cell 

 into four, one of which forms the foot. 



So far as I know, a budding similar to that in the cases described is 

 only mentioned by "VVigand, " Botanische Zeitung," Feb. 16, 1849, and 

 by him in language which, it must be confessed, is not a little obscure : 

 *' Eine beachtenswerthe Erscheinung begegnete mir bei einigen Exem- 

 plaren, niimlich eine Sprossenhilduiig, ungefahr an der Stelle des Lagers 

 wo das bebliitterte Pflanzchen angel egt wird, entspringen junge Vorkeime 

 von derselben Gestalt, wie die Hauptvorkeime im jungen Zustande, mit 

 dem verschmalerten Ende (dem Sporenende entsprechend), an dem 

 Lager festsitzend, spjiter sich losloseud und wie ein selbstaudiger Vor- 

 keim sich verhaltend." From the above paragraph, it Avould be, per- 

 haps, difficult to say whether Wigand had seen any thing similar to our 

 case. But, taken in connection with his Tafel 1, Fig. 25, where a pro- 

 cess 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 fimction of the fern-prothallus is very important. Since the publi- 

 cation by Leszcyc-Suminski, in 1848, of his observations concerning the 

 sexuality of ferns, the prothallus has been regarded as an organ interme- 

 diary between the spore and the fully developed plant, growing out of 

 the former, and bearing sexual organs which by mutual co-operation pro- 

 duce the latter. It has been considered impossible 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 unsexual as, for instance, the production of plantlets 

 on the fronds of Asplenium viviparum. This fact is an unexpected one 

 for those who constantly 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 



