OF THE IMPBOVKMENT OF KACES. 313 



and the Pear, or the Blackberry and the Easpb^ry,- 

 any of which might have been expected to intermix. 

 As to mules obtained between plants of distinct 

 genera, we have, no doubt, upon record, some experi- 

 ments said to have been performed successfully in 

 crossing a Thorn- Apple with Tobacco, the Pea with 

 the Bean, the Cabbage with the Horse-radish, and so 

 on; but Mr. Herbert regards these cases, and I think 

 with great reason, as apocryphal, and not to be relied 

 on ; the fact being, as he truly states, " that in this 

 country, where the passion for horticulture is great, 

 and the attempts to produce hybrid intermixtures 

 have been very extensive during the last fifteen years, 

 not one truly bigeneric mule has been seen." 



On the other hand, cross breeding (89) will take 

 place quite as readily among plants as among ani- 

 mals, and it is difficult to estimate the alteration 

 which this process has really produced, although 

 unperceived by us, in the amelioration and advantage 

 of long-cultivated plants. We cannot reasonably 

 doubt that a process so simple as that of dusting the 

 stigma of one plant with the pollen of another, which 

 must be continually happening in our gardens, either 

 through the agency of insects or the currents in the 

 air, and which, where it takes place between two 

 varieties allied to each other, must necessarily pro- 

 duce a cross, — we cannot suppose, I say, that this 

 occurs in our crowded gardens and orchards at that 

 time only when we perform it artificially. 



The operation itself) although so simple, consisting 

 in nothing more than applying the pollen of one 



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