204 PLANT HYBRIDIZATION BEFORE MENDEL 



line of descent is a continuous individual of idioplasm. In this case it is 

 nothing but the persistence of the organized substance in a changing 

 process of movement or the necessary passing over of one idioplasmatic 

 configuration into the next following. And it is not alone between the 

 ontogenetically different plant- and animal-individuals, but also within 

 these individuals everywhere present, where every individual part (cells, 

 organs) follows another in time. Heritable phenomena are such as of 

 necessity pass over to the following generations, and in general such as 

 have their seat in the idioplasm, since the non-idioplasmic substance is 

 only capable of continuing through a limited number of cell genera- 

 tions." (p. 542.) 



27. Treatise of W. O. Focke. 



The last of the hybridists of the older school who engaged in 

 extensive publication, was Wilhelm Olbers Focke, who published 

 in 1881, his 'Tflanzenmischlinge," a work of 569 pages (1), con- 

 sisting primarily of a systematic arrangement, according to or- 

 ders, families, and genera, of plant hybrids known to have been 

 produced by various experimenters up to his time, or reported 

 as having been found wild. This arrangement, while it made no 

 pretension to completeness, was yet the most thorough and exten- 

 sive single compendium of the kind yet published. 



"I have," he says, "so far as it was possible, examined the statements 

 met with, have not quoted the least credible at all ; others I have ac- 

 cepted as questionable, but, in the case of the most of the information, 

 I have had no reason for doubting the correctness of the observations, 

 even though, on the other hand, I could not regard them as confirmed 

 or sufficiently vouched for." (p. 3.) 



"At all events," Focke remarks, "through the present collection of 

 known facts, it will, as I think, be rendered essentially easier to find 

 the objects toward which future investigations concerning plant crosses 

 must be directed." {ib., p. 2.) 



In the case of most hybrids, especially those occurring wild, 

 Focke contented himself with brief references concerning their 

 occurrence, but entered into more extended consideration of the 

 more carefully investigated hybrids produced by hand-pollina- 

 tion. 



Focke himself was not extensively engaged in investigations in 

 hybridization. 



"To my regret," he says, "l have never been in a situation to institute 

 hybridization experiments on a large scale, nevertheless, through crosses 

 and breeding carried on by myself, I have at least gained some practical 

 experience, which should be of decided use for the estimation of the 

 statements of others." {ih., p. 3.) 



As to the results of his observations however, Focke came to 



