116 GOOD FROM CROSSING. Chap. XVII. 



and penetrating the stigma, so that the two poli en-masses, after an 

 interval of eleven days., could not be distinguished except by the 

 difference of their caudicles, which, of course, undergo no change. 

 Fritz Miiller has, moreover, made a large number of crosses between 

 orchids belonging to distinct species and genera, and he finds that 

 in all cases when the flowers are not fertilised their footstalks first 

 begin to wither; and the withering slowly spreads upwards until 

 the germens fall off, after an interval of one or two weeks, and in 

 one instance of between six and seven weeks; but even in this latter 

 case, and in most other cases, the pollen and stigma remained in 

 appearance fresh. Occasionally, however, the pollen becomes 

 brownish, generally on the external surface, and not in contact with 

 the stigma, as is invariably the case when the plant's own pollen is 

 applied. 



Fritz Miiller observed the poisonous action of the plant's own 

 pollen in the above-mentioned Oncidium flexuosum, 0. uniccrne, 

 pubes (J), and in two other unnamed species. Also in two species of 

 Eoclriguezia, in two of Notylia, in one of Burlingtonia, and of a 

 fourth genus in the same group. In all these cases, except the last, 

 it was proved that the flowers were, as might have been expected, 

 fertile with pollen from a distinct plant of the same species. 

 Numerous flowers of one species of Notylia were fertilised with 

 pollen from the same raceme ; in two days* time they all withered, 

 the germens began to shrink, the pollen-masses became dark brown, 

 in 1 not one pollen-grain emitted a tube. So that in this orchid the 

 injurious action of the plant's own pollen is more rapid than with 

 Oncidium flexuosum. Fight other flowers on the same raceme were 

 fertilised with pollen from a distinct plant of the same species : two 

 d: these were dissected, and their stigmas were found to be pene- 

 trated by numberless pollen-tubes ; and the germens of the other 

 six flowers became well developed. On a subsequent occasion many 

 other flowers were fertilised with their own pollen, and all fell off 

 dead in a few days ; whilst some flowers on the same raceme which 

 la I been left simply unfertilised adhered and long remained fresh. 

 We have seen that in cross-unions between extremely distinct 

 orchids the pollen long remains undecayed ; but Notylia behaved 

 in this respect differently ; for when its pollen was placed on the 

 stigma of Oncidium flexuosum, both the stigma and pollen quickly 

 became dark brown, in the same manner as it the plant's own pollen 

 had been applied. 



Fritz Miiller suggests that, as in all these cases the plant's own 

 pollen is not only impotent (thus effectually preventing self-fertilisa- 

 tion), but likewise prevents, as was ascertained in the case of the 

 Notylia and Oncidium flexuosum, the action of subsequently applied 

 pollen from a distinct individual, it would be an advantage to the 

 plant to have its own pollen rendered more and more deleterious ; 

 tor the germens would thus quickly be killed, and dropping off, 

 there would be no further waste in nourishing a part which 

 ultimately could be of no avail 



