96 The Individual Tracks 



and the Muscineae have in recent years repeatedly been 

 the subject of investigation, and the conviction has be- 

 come rooted in regard to them that, at least in some cases 

 of mutilation, every, or almost every cell that remains 

 unhurt can grow into a new individual. Pringsheim ex- 

 amined the mosses, Vochting the liverworts, Brefeld the 

 fungi/^ On continuing, under favorable conditions, the 

 cultivation of pieces cut off from these plants, one can 

 grow a new plant from every part that is not too small. 

 The stipe and the pileus of the fungi grow new pileuses 

 from the cut surfaces, the mosses form buds from any 

 given cell of the roots, leaves and shoot, even from the 

 sporangium and its stalk. At first the cells grow into the 

 thread-like protonema, on which the leaf-buds can then 

 develop in the usual manner. The Marchantiaceae, ac- 

 cording to Vochting, can be chopped up fine, and every 

 particle which has a sufficient number of uninjured cells 

 to keep it alive, will form a new plant. In the case of 

 Marchantia polymorpha I can confirm this observation 

 from my own experience. 



In these cases, therefore, all, or nearly all the ramifi- 

 cations of the cell-pedigree form either primary, or at 

 least secondary germ-tracks. Somatic, that is, necessar- 

 ily sterile twigs are possibly present, although it has not 

 yet been proven. This case, which for Weismann forms 

 an exception, and demands a special assumption for its 

 explanation,^^ is for us only an extreme one in the rich 

 abundance of examples. 



iiPringsheim, N. Ueber Sprossung der Moosfriichte. Jahrh. 

 Wiss. Bot. 11: 1. 1878. 



Brefeld, O. Botanische Untersuchungen ilber Schimmelpilze, 

 Vol. I. Vochting, H. Ueber die Regeneration der Marchantiaceen. 

 Jahrh. Wiss. Bot. 16: 367. 1885. 



12 Weismann, A. Die Kontinuitdt des Keimplasmas. p. 68. 



