PLANT CHIMERAS 133 



particular arrangement the term Peridural chimcera has been 

 adopted. 



Let us see in what way this knowledge helps us to explain 

 the peculiarities of these plants. In the first place, the particular 

 form will resemble the one or other parent more closely, as the 

 one or other parent enters more largely into its composition : 

 a reference to the characters and structure of tubingense and 

 Kcclreuterianum shows this to be the case. Secondly, the 

 phenomenon of vegetative throwbacks is readily understood 

 when we see that a slight accidental injury or derangement of 

 the tissues of one partner will permit of the appearance of the 

 other in its pure state : this is, of course, more particularly the 

 case with adventitious buds, arising from a wounded surface. 

 And, finally, the fact that the intermediate form always breeds 

 true to one parent becomes self-evident when we remember 

 that the sex-cells are always produced from the sub-epidermal 

 layer, and therefore always belong to the one parent : that the 

 chimaera is sterile with the other parent is explained by the 

 same considerations. The parent to which the seeds of the 

 chimaera revert will be the parent which constitutes the sub- 

 epidermal layer, and this is in fact the case. 



This explanation is admirably simple : can it be applied to 

 these original " graft hybrids," the origin of the whole discussion ? 

 Anatomical investigation has shown that it can. The arrange- 

 ment of the pigments in the petals of Cytisits Adami shows that 

 that shrub is a chimaera, which consists of a core of laburnum 

 with an epiderm of purple broom. The characters of the 

 epiderm and cortex of the fruit of Cratcegomespilus asniersii prove 

 it to be a hawthorn with the skin of a medlar. Minute investi- 

 gations of the anatomy of various other parts of the two plants 

 have only confirmed these results. And we recall the fact 

 that the two seeds which C. Adami bore both grew up into 

 laburnums. 



The uniformity of these results is broken only by Solatium 

 Darzvinianum, the nature of which is not yet clear. Prof. 

 Winkler states that it is not a periclinal chimaera, and has 

 promised further investigations : pending the publication of 

 these, we cannot say how it is built up. 



The theoretical interest of these results is of course very 

 great. A very awkward exception to various laws of heredity 

 has been removed. The opening paragraphs of a new chapter 



