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134 



GOOD FROM CROSSING. 



Chap. XVII. 



houses, I concluded without hesitation that their self-sterility was due to 



cause 



Miiller 



fertilised above one hundred flowers of the above-mentioned Oncidiu 



exuosum* w 



is 



there endemic. 



m 



own 



i\ 



lids o 



rom distinct plants ; all the former were sterile, whilst those fer- 



from any other plant of the same species were fertile 

 first three days there was no difference in the action of the two 

 f pollen : that placed on the stigma of the same plant separated in 

 usual manner into grains, and emitted tubes which penetrated the 

 column, and the stigmatic chamber shut itself; but the flowers alone 

 which had been fertilised by pollen taken from a distinct plant produced 

 seed-capsules. On a subsequent occasion these experiments were repeated 

 on a large scale with the same result. Fritz Miiller found that four other 

 endemic species of Oncidium were in like manner utterly sterile with their 

 own pollen, but fertile with that from any other plant: some of them 

 likewise produced seed- capsules when impregnated with pollen of widely 

 distinct genera, such as Leptotes, Cyrtopodium, and Rodriguezia ! Onci- 



dium crispum, however, differs from the foregoing species in varying much 

 in its self-sterility; some plants producing fine pods with their own pollen, 



others failing to do so ; in two or three instances, Fritz Miiller observed 

 that the pods produced by pollen taken from a distinct flower on the same 

 plant, were larger than those produced by the flower's own pollen. In 



hi 



t> iii t> 



family, fine pods were produced by the plant's own pollen, but they con- 

 tained by weight only about half as much seed as the capsules which had 

 been fertilized by pollen from a distinct plant, and in one instance from 

 a distinct species ; moreover, a very large proportion, and in some 

 nearly all the seed produced by the plant's own pollen, was embryon- 

 less and worthless. Some self-fertilized capsules of a Maxillaria were in a 



similar state. 

 Another observation made by Fritz 



is highly remarkable, 



.. ^^^^.^, ^,j j-j.xu.Ci -LI-LI*! J.CL J.O U-lglllJ J. OJ-UCU. U.CI U.HJ, 



namely, that with various orchids the plant's own pollen not only fails 

 to impregnate the flower, but acts on the stigma, and is acted on, in an 

 injurious or poisonous manner. This is shown by the surface of the 

 stigma in contact with the pollen, and by the pollen itself, becoming in 

 from three to five days dark brown, and then decaying. The discoloura- 

 tion and decay are not caused by parasitic cryptogams, which were 

 observed by Fritz Miiller in only a single instance. These changes are 

 well shown by placing on the same stigma, at the same time, the plant's 

 own pollen and that from a distinct plant of the same species, or of 

 another species, or even of another and widely remote genus. Thus, on 

 the stigma of Oncidium flexuosum, the plant's own pollen and that from a 

 distinct plant were placed side by side, and in five days' time the latter was 

 perfectly fresh, whilst the plant's own pollen was brown. On the other 

 hand, when the pollen of a distinct plant of the 



and of the Epidendrum 



flexuosum 



(nov. spec. ?) 



same stigma, they behaved in exactly the same manner, the grains 

 separating, emitting tubes, and penetrating the stigma, so that the two 





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