LIFE AND DEATH. 281 



affected by external stimuli, as evinced by some 

 of the phenomena of hybridisation and of cross- 

 and self-fertilisation, because we find the results 

 expressed in the mingling of the characters of 

 parents, in strengthened or enfeebled progeny, 

 and even in the appearance of unexpected pro- 

 perties, which, from the facts of Reproduction, 

 we know must have taken their origin in some 

 alteration of the nuclear substance of the embryo. 



Here, however, we know in most cases that the 

 principal agent which has reached the nuclear- 

 protoplasm, is another portion of nuclear-proto- 

 plasm. In hybridisation, one which has been 

 fed and influenced by cell-protoplasm of a very 

 different plant ; in cross-fertilisation, one fed and 

 influenced by the cell-protoplasm of a different 

 plant of the same species, and in self-fertilisation, 

 one fed and influenced by the same cell-proto- 

 plasm. 



That somewhere, and somehow, such nuclear- 

 protoplasm as induces the changes in the char- 

 acters of hybrids, etc., has been influenced by its 

 immediate environment the cell-protoplasm of 

 the plant appears to be a conclusion from which 

 there is no escape. We may obtain similar 

 evidence from the experience of grafting. It is 

 relatively easy to influence the cell-protoplasm of 

 a scion by a suitable stock, obviously because the 

 latter, while handing on to the former all necessary 

 materials from the soil, presents the indispensable 

 elements and compounds in somewhat different 

 proportions, dilutions, etc., from those which its 



