174 Staten Island Association of Arts and Sciences 



had been found by close observation in the field. In reply to the 

 question whether the limits of variation of these hybrids had 

 been closely studied, and whether the hybrids showed as great 

 variation as the putative parents, it was stated that the hybrids 

 showed a wider range of variation. In some cases it would be 

 difficult to state the correct relationship of a probable hybrid with- 

 out having a number of fronds from the same plant or from 

 similar plants. In this connection it should be stated that when 

 a specimen shows undoubted close relationship to two different 

 species and stands intermediate in characteristics, sharing the 

 characteristics of the two species, it is very likely that the speci- 

 men in question is a hybrid between the two species whose char- 

 acteristics it shares, and we are justified in describing it as a 

 hybrid. If some one else chooses to describe the specimen in 

 question as a species, or wishes to consider a hybrid a species, 

 he may be entitled to his view. But if he denouces these hybrids 

 as such because they have not been artificially produced and thus 

 have not been proved to be hybrids let him also prove that they 

 are not hybrids. He showed also a diagram representing the fif- 

 teen possible hybrids between six species of Dryopteris, thirteen 

 of which he had seen (marked with the -\- sign) and eight of 

 which had been described (marked with ++)• 



