346 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN 



(b) That the pistils and pollen tubes of any one plant possess 

 the same "individual stuff"; and 



(c) That the best growth of pollen tubes is made when they 

 penetrate into stigmas having another kind of individual stuff. 



In respect to the "individual stuff" there is, it is assumed, a 

 differentiation between individuals quite analogous to that which 

 the chemical theory of species assigns to different groups of 

 organisms. In the single individual, however, parts so anato- 

 mically differentiated as sex organs are assumed to possess the 

 same individual stuff. Thus the distribution of the "stuff" is 

 entirely independent of any distribution of formative stuffs in 

 organogenesis as Sachs conceived it, or of segregations of germ 

 plasm units in development (in Weismann's sense), in the reduc- 

 tion process of sporogenesis, or of the degree of organ specificity 

 that may exist. In spite of all known anatomical and physi- 

 ological differentiation of the organs concerned, there is, it is 

 assumed, a lack of differentiation in respect to the distribution of 

 the particular mdividiial stuff. 



Jost's general theory minimizes the significance of fluctuating 

 variation in self-sterility, although he was fully aware that such 

 variations appear. In 1905, ninety-three autogamous pollina- 

 tions with Corydalis cava gave six capsules, an evidence that all 

 plants of this species are not absolutely self-sterile. That the 

 operation of any assumed individual stuffs is fluctuating is also 

 apparent from Jost's careful studies of rye {Secale cereale). Ulrich, 

 especially, had already shown three varieties to be feebly self- 

 fertile, and that varietal and individual differences exist, so that 

 Jost remarks "W'ir sahen schon bei Corydalis, dass diese Pflanze 

 wahrscheinlich nicht absolut selbststeril ist. Es ist wohl moglich, 

 dass es absolut selbststerile Pflanzen iiberhaupt nicht gibt" ('07, p. 

 89). Jost's own studies on Secale were with a race known as Secale 

 montanum, in which from many isolated heads he obtained only 

 three seeds, one of which contained an embryo. The results of 

 careful studies showed that in this variety pollen tubes from 

 xenogamous (pollen from another plant) pollination penetrated 

 to the micropyle in seven to nine hours, while tubes from auto- 

 gamous pollination after twenty-four hours had only reached the 

 base of the pistil. From certain of the experiments it appears that 

 tubes from geitonogamous (pollen from another flower of the 



