636 Vehicles of the Hereditary Characters. 



The second part of Darwin's Pangenesis is met by 

 insuperable difficulties, and has long since been regarded 

 as superfluous. Darwin himself admitted that it had 

 only a very limited application to plants and corals, to 



Fig. I-14. Ulmus campestris varie- 

 gatiis. The variegated regions 

 are developed in widely differ- 

 ent extents on the different 

 leaves. 



Fig. 145. Beta vulgaris saccha- 

 rifcra. A chance \ariegated 

 leaf. The yellow and green 

 tissues are superimposed upon 

 one another in such a way 

 that the limits of the indi- 

 vidual layers do not corre- 

 spond. 



investigations of Bonnier and Flot. See G. Bonnier, Formation 

 des elements du cilindre central, Comptes rendus, Vol. CXXXT, p. 

 781 (Nov. 12, 1900), and Sur la differenciation des tissus vascii- 

 hires, loc. cit., p. 1276 (Dec. 1900) ; and Leon Flot, Sur I'origine 

 commune des tissus dans la feuille et dans la lige, loc. cit. (Dec. 1900). 



