PLANT HYBRIDIZATION BEFORE MENDEL 267 



On the matter of the constitutional vigor of hybrids, the case 

 is cited of Monthretia crocosmaeflora, a hybrid between Mont- 

 hretia pottsii and Tritonia aurea.^ 



During the winter of 1890-91 the corms of M. pottsii were 

 scarcely injured; those of Tritonia aurea only survived where 

 planted against the outer side of a hothouse. The corms of the 

 hybrid survived to the extent of 60 per cent. 



In 1892, Macfarlane published the final results of his studies 

 on the microscopic structure of hybrids, in the Transactions of 

 the Royal Society of Edinburgh. (6e.) 



This memoir was published as the conclusion of a series of 

 studies of the microscopic structure of upwards of sixty hybrids, 

 in comparison with that of their parents. The details are given 

 with respect to nine hybrids and their parents, as follows : 



Philageria veitchii {Lapageria rosea X Philesia buxifolia) (species from 

 southern Chile) 



Dianthus grievei (D. alpinus X D. harhatus) 



Geum intermedium (G. rivale X G. urbanum) 



Ribes culverwellii (R. grossularia X R- nigrum^ 



Saxifraga andrewsii (S. aizoon X 5. geum) 



Erica watsoni (E. ciliaris X E. tetralix) 



Bryanthus erectus (Menziesia empetriformis, var. drummondii X Rhodo- 

 dendron Chamaecistus) 



Masdevallia chelsoni (M. amabilis X M. veitckiana) 



Cypripedium leeanum {C. insigne X C. spicerianum) 



In addition, he says, "about sixty-five hybrids and their 

 parents have been examined in some of their parts," to which 

 partial reference is made as to special particulars. An elaborate 

 study is also given of the well-known graft-hybrid Cytisus adami^ 

 the accidental result of a case of the budding of Cytisus pur- 

 pureus upon the stock of Cytisus laburnum {^Laburnum vulgar e)^ 

 a type for which no equivalent sexual hybrid exists, all attempts 

 to cross the two species sexually having failed. Cytisus purpureus 

 is a low, creeping, and C. laburnurrk an upright shrub. C. pur- 

 pureus grows, when grafted upon C. laburnum^ as well as, or 

 better than upon its own roots. Thousands of grafted plants give 

 only normal, upright-growing forms of purpureus. In M. Adam's 



1 Montbretia is a synonym of Tritonia, a group of thirty South African 

 bulbous plants of the Iridaceae, belonging to the Gl«dioleae, of the 

 sub.-fam. Ixiodeae. 



