344 TricotyloHS Races. 



manifested than the other. ^Moreover those cases would 

 have to be excluded in which either the conditions of 

 life or some selection of the race could have exerted an 

 influence in one direction or the other; for, as we have 

 seen, intermediate races are very susceptible to both these 

 groups of factors. 



Among the intermediate races known to me the tri- 

 cotylous and syncotylous forms approach most closely 

 this ideal picture.^ For, in pure cultures, they furnish 

 as a rule 50% dicotylous and 50% tricotylous or syn- 

 cotylous seedlings. By altering the conditions of growth 

 as well as by selection this proportion can be easily and 

 greatly modified in both directions, almost to the ex- 

 clusion of one or other of the two types. But such treat- 

 ment leaves the essential nature of the intermediate race 

 untouched. It neither reverts to the half race when 

 subjected to selection, nor is it possible to derive a con- 

 stant and pure tricotylous variety from it.- 



As far as I know, there are hardly any references 

 to tricotylous races in botanical literature, and the possi- 

 bility of the existence of tricotylous intermediate races 

 seems never to have been discussed. In this part, how- 

 ever, I shall describe some instances of such races in 

 order to demonstrate their existence and to study their 

 characters. In the period from 1892 to 1897 I succeeded 

 in producing such races from half a dozen very different 

 species. 



I wanted also to include in this inquiry some pure 

 tricotylous and pure dicotylous races, that is to say, 

 races the seedlings of which were in the first case ex- 

 clusively tricotylous and in the latter exclusively dicotyl- 



^ See my preliminary note Ueber tricotyle Rassen in Ber. d. d. 

 bot. Ges., 1902, Vol. XX, p. 45. 

 ^ See the scheme on page 24. 



