I). J. BCOURFIELD ON MEKDELISM AND MICROSCOPY. 



, 11 the hybridisation of various plants, more especially peas, which 

 [ed him fco the enunciation of the law now associated with his 

 name. For more than ten years lie quietly pursued the somewhat 

 monotonous work of tending and recording the results from many 

 thousands of plants raised in the garden attached to the 

 monastery, and in 1865 his now famous paper, " Yersuche iiber 

 Pflanzenhybriden " ("Experiments on Plant Hybrids"), was read 

 before and published in the Transactions of the Briinn Natural 

 TTistory Society. In 1869 he published in the same Transactions 

 ;i small paper on Ilawkweed hybrids, but this did not tend to the 

 further elucidation of the subject. About this time Mendel 

 became Abbot of Briinn, and apparently found but little leisure to 

 continue his experiments — at least, he did not publish anything 

 further on the subject. He died in 1884. His work on plant 

 hybrids did not attract any particular attention amongst his con- 

 temporaries, and was soon completely forgotten, only being 

 brought to light again by the remarkable simultaneous and 

 independent researches of three Continental botanists, De Vries, 

 Correns aermak, in 1900. 



Y\ e will now consider a little more closely what Mendel did. 

 His efforts were directed essentially to the discovery of the 

 number of forms which hybrids between different races of plants 

 could assume, and the numerical relation existing between those 

 forms. It is important to note that Mendel used the word 

 " hybrid " for a cross between two races, even if only separated by 

 gle character, as well as for a cross between two species. 

 The word will also be used in this extended sense in this paper. 

 The method by which Mendel endeavoured to get his results was 

 to follow up the development of the hybrids in their progeny, and 

 he saw quite plainly that three important conditions would have 

 to be complied with in order to get clear answers to his problems. 

 These were (1) the employment of suitable objects for experiment ; 

 (2) the keeping of separate records of the results obtained by 

 ] .laming every individual seed produced during several generations ; 

 and (3) the fixing of the attention upon certain selected characters 



the exclusion of all other considerations. 



As regards the first point Mendel laid it down as evidently 

 necessary that plants suitable for such an investigation as he pro- 

 posed must possess constant differentiating characters; that the 

 hybrids from Mich plants must, during the flowering period, be 



