342 



C. SKOTTSBERG 



The fact that IRMSCIIER tried to prove that the distribution of plants strongly 

 supports Wegener's hypothesis does not lessen the value of what he says about 

 the limited capacity of plants to migrate. It is small in the flowering plants {143. 291): 



Dass bei den Blutenpflanzen die Beforderung der Samen und Friichte durch Wind, 

 Wasser und Tiere ganz wesentlich eingeschrankt werden muss und fiir geschlossene 

 Forniationen auf grossen Entfernungen bin nicht in Frage kommt, ist heute von den 

 Pflanzengeographen allgemein anerkannt. 



■ Irmscher is too optimistic, we have seen that there are phytogeographers 

 to whom overseas migration is not only possible and undoubtedly happens, on 

 rare occasions at least, but rather of quite common occurrence. And with regard 

 to spore-plants their distribution should, if this be correct, show quite different 

 distribution patterns than they actually do. The bryophytes are no exception to 

 the rule. IRM.SCIIER remarks that already in 1903 Stepiiani denied that liverworts 

 are able to make long and successful jumps. Attention should be paid to Domin's 

 valuable paper [yd] in whicli he brings together numerous facts illustrating the same 

 definite distribution patterns in this as in other groups, and Miss FULFORD (e.g. 

 103) has arrived at the same conclusion. We know that the spores, in many cases 

 at least, are extremely sensitive to changed conditions and lose their viability 

 very rapidly when exposed to the air — a promising field for experiments. Regard- 

 ing mosses I refer to Herzog's work {i2g) where he speaks against the belief in 

 the importance and great range of dispersal through the air. We find, Irmsciier 

 says, the same disjunctions, the same part areas (Teilareale) in angiosperms, 

 gymnosperms, ferns and bryophytes, and he continues p. 292 : 



Dass diese vier in ihren Verbreitungsmitteln so verschiedenen Pflanzengruppen die- 

 selben Verbreitungszuge ihrer Disjunktelemente ergeben, zeigt wohl einwandfrei, dass 

 hierfiir der "Wind" ebenso wie andere aussere Krafte als Ursache abzulehnen sind. 

 Wiiren sie in ausschlaggebender Weise an der Ausbreitung beteihgt, miisste die Resie- 

 delung entsprechend der Verschiedenheit der Friichte, Samen und Sporen ebenso ver- 

 schiedenartig ausgefallen sein, d.h. in den einzelnen Gruppen dieser biologischen Ver- 

 schiedenheit entsprechende charakteristische Merkmale zeigen. Dies ist aber nicht der 

 Fall. Der alien vier Gruppen g e m e i n s a m e n hochdisjunkten Ausbildung so vieler Areale 

 muss vielmehr eine andere Ursache zu Grunde liegen . . . 



This common cause was, in Irmscher's opinion, continental displacement in the 

 sense of W'EGENER. Those who disagree with him will have to look for vertical 

 movements, emergence and submergence of land. 



Lichens, fungi etc. were not included in Irmscher's discussion. A survey of 

 their distribution patterns is something to be asked for. Lichens are said to de- 

 pend on their vegetative reproduction bodies more than on spores. 



It is maintained that, with certain exceptions, terrestrial animals spread 

 less easily than plants. I have consulted a number of zoogeographers in order to 

 learn their opinion on the mode of transport likely to be used by invertebrates 

 in their supposed ocean voyages. Birds etc. are left aside here. 



Numerous insects, butterflies, moths, flies, hymenoptera, grashoppers, cock- 

 roaches, as well as spiders, myriapods, etc. follow man from land to land, from 

 island to island. This is, I daresay, the only safe way for such animals to get 



