COMBINATION OF PARENT-CHARACTERS. 561 



succeeded in producing in Breslau a compound hybrid in which were united Salix 

 Caprea, S. daphnoides, S. La2?ponum, S. purpurea, S. Silesiaca, and iS*. viminalis. 



It need hardly be said that the characteristics of the six ancestral species in such 

 a case as that of the last-mentioned hybrid are not easily identified. Even where 

 a hybrid is the offspring of a single cross between two species it is not always easy 

 to determine its origin from its external appearance, and in the absence of any 

 knowledge of the history of its production. The characteristics of the parent-stocks 

 are not combined in all hybrids according to a single definite rule. Sometimes the 

 combination seems to amount to a complete fusion, so that the form produced might 

 be compared to an alloy of two metals. Very often a new form is generated which 

 combines in a definite geometrical ratio the characteristics of the parents in respect 

 of the position and direction as well as the shape and size of its separate parts. In 

 that case there is said to be a union of the parental characters. The structural 

 characters of both stocks are represented unmodified, but are so closely bound 

 together as to suggest a composite crystal founded upon two different crystalline 

 forms. Just as in definite combinations of crystals the faces of one component form 

 are dominant, and determine the general aspect in one case and those of the other 

 component form in another case, so in many hybrid plants sometimes the attributes 

 of the one parent, sometimes those of the other, are most conspicuously reproduced. 

 Other hybrids again are analogous to combinations in which both crystalline forms 

 are equally represented. Again, in addition to the above classes of hybrids 

 wherein the parental characters are either completely merged together or intimately 

 united there are many cases where those chai-acteristics are present almost un- 

 changed, and subsist side by side like the particles of a rock. The most common 

 case of this mixture or juxtaposition of properties occurs where the hybrid displaj-s 

 hairs, glands, or prickles of two forms interspersed together, one of which is identical 

 with the form of the structure in question exhibited by the maternal stock, whilst 

 the other has been inherited unchanged from the paternal stock. Or, one part of 

 the hybrid's flower may be coloured like one parent and another like the other 

 parent. Hybrids are also known in which the foliage is almost indistinguishable 

 from that of one parental stock whilst the flowers are like those of the other, so that 

 at first sight a hybrid of the kind looks as if it were a plant of the former species 

 with flowers of the second species afiixed to it for a joke. On closer inspection some 

 slight difierences may be perceived between the leaves and flowers of the hybrid and 

 those of the parent species respectively, but this does not alter the fact that hybrids 

 exist whose leaves resemble far more closely those of one parent, whilst their 

 flowers are more like those of the other. Probably it was the occurrence of such 

 a hybrid which suggested the proposition referred to on p. 557 that in the product 

 of a cross between two species the flowers reveal the paternal and the foliage the 

 maternal stock. But this statement is incorrect, as was said before, for some 

 hybrids approximate to the maternal stock in respect of their flowers, and to the 

 paternal stock in fespect of their leaves. 



Of the three ways in which the parental characters may be combined in a 



VOL. n. 86 



