84 REGENERA TION 



itself is that the result may be in some way connected with the hard 

 cell walls in plants that make difficult the organization of large areas 

 into a new whole. As a result, the new development takes place in a 

 small group of similar cells, that are sufficiently near together to 

 organize themselves into a whole despite the interference met with in 

 the cell walls. 



Vochting has also studied the regeneration of pieces of the liver- 

 wort, Lnmilaria vnlgaris. The results have been already partly given 

 in the first chapter. If cross-pieces are taken from the thallus, each 

 produces a new bud at its anterior or apical end (Fig. 9, A, A ! ). The 

 new bud arises from the cut-surface, or very near it, from a group of 

 cells of the midrib that lies nearer the under side (Fig. 9, A 2 ). The 

 bud gives rise to a new thallus that springs from a narrow base at its 

 origin from the old piece. If a piece is cut longitudinally from the 

 thallus along the old midrib, the new bud arises at the anterior end 

 from the midrib (Fig. 9, B\ It comes either from the anterior cut- 

 surface near the inner edge, or from the anterior end of the inner 

 edge, and in some cases two new buds arise, one at each of these 

 places. If the piece is removed from one side of the midrib it does 

 not regenerate as quickly as when a part of the midrib is present, but 

 when the new bud develops it arises from the anterior part of the 

 inner edge (Fig. 9, B 1 ). If the piece is cut far out at one side, it may 

 be a long time before the new bud arises. This difference in the rate 

 of development of these pieces is explained by Vochting as due to the 

 simpler character of the cells near the midrib. 



If oblique pieces are cut off, with an anterior oblique cut-edge, as 

 shown in Fig. 9, C, C 1 , the new bud arises along the anterior surface. If 

 the piece includes a portion of the old midrib at its inner end, the new 

 bud arises from this (Fig. 9, C), but if the piece lies to one side of the 

 midrib, the new bud arises near the anterior end of the anterior 

 oblique surface (Fig. 9, C 1 , C 2 ) 



A number of experiments that were made in order to determine 

 what part gravity and light may take in the regeneration gave nearly 

 negative results. The regeneration appears to result largely from 

 internal factors. 



If a piece of the thallus is divided parallel to its surface, the two 

 parts may each produce a new thallus, but this arises much more 

 readily from the lower piece. If a piece of the latter is cut into 

 small pieces no larger than half a cubic millimetre, and even much 

 smaller, each may produce a new thallus. 



Vochting also studied the regeneration of parts having a limited 

 growth. If a gemmiferous capsule is cut off, then split into two or 

 four pieces, and these are placed on moist sand, it is found that new 

 buds arise along the basal cut-edge. In order to show that this is 



