HYBRIDISING AND CROSS-BREEDING. 1 19 



masses, and where fertilisation cannot take place except by 

 insect agency or by direct artificial means, are the most trust- 

 worthy, for reasons already explained. We. have several Orchids 

 imported from abroad which are supposed to be natural 

 hybrids, such as Phalcznopsis roseo - Schilkriana (P. Veitchii, 

 Hort.), P. Schiller ianoamab alls (P. leucorrhoda and P. Casta, 

 Hort), P. roseo-amabilis (P. intermedia and P. intermedia 

 Portei, Hort.) There are also several Odontoglots of the O. 

 crispum and O. Pescatorei group, and others of the O. gforiosum, 

 O. n&vium, and O. triumphans types, which are presumably 

 natural hybrids, just as the forms of each, technically known 

 as " good " and " bad " varieties, are known to be the result of 

 seminal variation. Now, if we give the hybridiser the supposed 

 parents of any of our supposed natural hybrid Orchids or other 

 plants, and he produces us hybrid offspring like our presumed 

 hybrids as imported, we have, of course, good proof of the 

 fact hitherto only supposed ; and artificial hybridism, if thus 

 intelligently and carefully employed (aided sometimes by graft- 

 ing), becomes a blessing to the systematic botanist, instead of 

 the curse which the older professors wrongly anticipated. If 

 due care is taken, and experiments are conducted in an intelli- 

 gent and systematic manner, the producer of the commonest 

 florists' flowers may also contribute his mite to the store of 

 organised knowledge, and thus illustrate the force of the rule 

 that science and practice should go hand in hand. 



Sexual or Elective Affinity. Now, as when Gaertner wrote 

 nearly thirty years ago, we know comparatively nothing as to the 

 causes or conditions on which the power to produce generic 

 or specific hybrids depends. Some species which closely re- 

 semble each other in general appearance and time of blooming 

 will not blend ; while others widely different in habitat, time 

 of flowering, colour, and other particulars, mix very readily. 

 The species of Rhododendron, Calceolaria, Pelargonium (not 

 Geranium), and Dianthus have great elective affinity, and 

 reciprocal unions may in nearly every instance be made. 

 Evergreen Rhododendrons mix with deciduous Azaleas, and 

 shrubby Calceolarias reciprocally with the herbaceous species ; 

 yet, as Gaertner observes, the aptitude amongst species even 

 for union is scarcely ever present in an equal degree, nor is 

 it necessarily reciprocal, but greater or less on one side than 

 the other. The number of perfect seeds produced and the 

 vigour of the resulting offspring may be taken as a tolerably 

 safe index of the affinity between either genera or species ; and 

 where sexual affinity is entirely wanting on the one hand, the 

 production of fertile seeds is but rarely carried out, and the 



