HYBEIDIZING. 109 



certain laws must be complied with ; but which, to speak frankly, we attach less 

 importance to, as the results are often of the most contrary character. One or two of 

 these laws are however, so natural, that they cannot give rise to the smallest doubt. 



1. No plants which do not belong to the same natural order, can by any 

 possibility be made to intermingle. The absurd stories related of the origin of 

 Willmore's Double Pelargonium ( Surprise J, which was said to be a mule between 

 a Geranium and a Hollyhock, and of some other hybrids, need no refutation. 



2. No plants, which do not form part of the same genus, can be united by cross- 

 breeding. This law may at first sight appear to admit of many exceptions ; but it is 

 highly probable that, in many instances in which a reputed union has taken place 

 between plants of two distinct genera, a further examination would prove that the 

 two genera had been improperly separated, and did, in reality, constitute but one. 

 Should, however, the statement with regard to the recently originated Cheiranthus 

 Marshallii, which is said to be the offspring of the Cheiranthus ochroleucus, crossed 

 by the pollen of Erysimum Perofskianum, prove true, this law would have to be 

 relinquished, for of the wide distinction between these two genera, there is no 

 doubt whatever. 



3. Even among species belonging to the same genus, it is only those of similar 

 structure which will yield hybrids. Thus the Gooseberry and Currant, though both 

 belonging to the genus Ribes, have never been made to unite. It has been supposed 

 that union can only take place between those species in which the pollen grains are 

 of the same size ; and should this supposition be confirmed, a preliminary microscopic 

 examination of the two varieties of pollen, would enable us to judge of the 

 probability of obtaining hybrids between any two species. 



Where no natural hindrance exists to the union, the following precautions are all 

 that are necessary to success. 



1. The anthers or pollen bags of the plant which we desire to impregnate 

 artificially, should be removed immediately on the expansion of the flower; or, if when 

 this takes place, they are already burst, it will be necessary to open the flower 

 prematurely, for it is essential to success that the anthers should be cut out before 

 their pollen is ripe. In some of the Campanulas the anthers burst previously to 

 the opening of the flower, and also in some of the Cytisus family, and probably in 

 many others. 



2. AVhen the anthers have been thus extracted, the stigma of the flower must be 

 carefully preserved from accidental impregnation by insects or other means, until it 

 is in a fit state for the reception of the pollen of the species with which we desire 

 to hybridize it. This end is best attained by tying a piece of fine muslin over the 

 branch on which the blossom is situated. It is usually easy to perceive the proper 

 moment for the application of the pollen, for the stigma, in most instances, 

 exudes a viscid fluid; and in those plants in which it is divided into lobes at its 



