436 Scientific Proceedings, Royal Dublin Societ//. 



mit Nahrsalzen vou massgebeuder Bedeutung ist." And this fact just 

 mentioned of the increase under conditions favouring transpiration of 

 mechanical tissue — collenohyma, bast, sclerenchyma — seems to speak very 

 directly against the " Grad der Inanspruchnahme " theory, and in view of 

 a more indirect working of transpiration. 



Again, transpiration itself, not to mention the "Inanspruchnahme" 

 tlieory, seems to have no bearing on sucli phenomena as the appearance of 

 small rings for some years in stumps of firs, pines, and larches. (See 

 Kuster (23) and Jost (28) for literature, most of wliich was inaccessible to 

 me.) Here, too, may be mentioned the development of wound wood, and 

 especially such developments of it as are referred to by Simon (22). Thus a 

 large callus witli wound wood wns formed on the outer surface of a Populus 

 canadensis twig. Some mras. down a horizontal hole was bored into the 

 pitli. This hole soon filled with callus. The wound wood in this callus 

 joined veith that of tlie external callus by bands of vessels which were 

 formed in the normally difPerentiated medulla. Such phenomena still 

 require an explanation. 



Again, Winkler supports his contention of the all-importance of trans- 

 piration with an appeal to the formation of annual rings. To go fully into 

 the present state of knowledge as to the origin of annular rings is hardly 

 in place here. The inaccessibility of the literature in any case would make 

 a critical discussion impossible, but the following three quotations seem to 

 me to mean that the question is still very much sub judice, and that indeed 

 one brings it up in a transpiration question at one's own risk. Thus 

 Haberlandt (15), in spite of the fact that he has been mentioned by Winkler 

 as supporting the transpiration theory of annular rings, say.s (p. 617) : — 

 " Eine entwicklnngsmechanische Erklarung der Jahresringbilduiig halte ioli 

 mit Krabbe und Jost derzeit fur unmoglich. Die ver.'^chiedene Ausbildung 

 von Friihlings — und Herbstholz ist in dieser Hinsicht mit anderen periodisoh- 

 wechselnden Wachstumserscheinungen auf gleiclie Stufe zu stellen, in 

 (leren Mechanik uns vorlaufig nicht der geringste Einblick gegonnt ist." 

 PfefTer (25) says, p. 216 : " The annual series of changes in the structure of 

 the wood is the result of a complex correlative reaction wliich we are not at 

 present able to resolve into simpler factors. Indeed, to do this, we must 

 first know the causes which determine the differentiation of equipotential 

 meristem cells." And Jost (21, p. 476) : " Die ' Beziehungen,' die zwischen 

 Jahresring und Jahrestrieb bestehen, brauohen aber nicht, Korrelationen zu 

 sein derart dasz die Blattbildung direct auf Friihjahrsholzbildung hinar- 

 beitet, es konnen auch beide Erscheinungen auf gemeinsamen Ursaohen 

 beruhen, Ursacheu die bewirken das nach einer gewissen Eiiheperiode ein 



