346 COULTER— INHERITANCE THROUGH SPORES. 



cell divisions is rapid. The fact that such plants can be induced to 

 form spores contrary to their normal habit, indicates that the con- 

 ditions of spore formation can be determined. These conditions 

 are described as yet in terms so vague that they mean little more 

 than environment, and this may be external or internal, depending 

 upon whether one speaks from the standpoint of the plant or of the 

 protoplast. Experimental work has shown that a spore may be 

 defined as a protoplast, usually separated from its old wall, always 

 separated from organic connection with other protoplasts, and by 

 virtue of this latter fact, capable of producing a new individual. 

 If this is a spore, what is a sexual cell which may be derived from 

 the same protoplast? Neither of them is a protoplast of special 

 cell lineage, as has been proved by inducing spore formation and 

 gamete formation in any cell lineage. 



The plant geneticist may not be interested in the conditions that 

 result in gamete formation, and even less interested in the condi- 

 tions that result in spore formation, but these are fundamental to 

 the problem of reproduction, and therefore fundamental to the prob- 

 lem of inheritance. A practical plant-breeder may be interested 

 only in the fact that he can obtain a new individual from a seed, 

 the pedigree of whose embryo in the nature of things cannot be 

 demonstrated, but only inferred ; but a scientific plant-breeder, whom 

 we now call a geneticist, must be interested in the conditions that 

 determine inheritance, and these include the conditions that deter- 

 mine reproduction in general. 



No more favorable material for determining the fundame\ital 

 facts of inheritance can be found among plants than spores of the 

 simpler forms. They are accessible, and therefore capable of con- 

 trol ; a succession of spore-produced individuals represents a line 

 whose purity cannot be questioned ; the so-called " modification of 

 the germ plasm " can be accomplished with a precision that is 

 impossible in an ovary and ovule-enclosed Qgg, to say nothing of 

 the sperm. In short, freed from all entanglements of sex, the pos- 

 sibiHties of variation in pure lines can be determined, and the pos- 

 sibilities of the inheritance of such variations. Such work will 

 establish the facts common to all inheritance, and will enable us to 

 recosrnize the contribution of sex to inheritance. 



