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;and seem to forin two distinct and natural groups. 

 Hybrids between these two new genera are peculiarly 

 interestinj;, inasmuch as the former has a one-celled 



•ovary, while the latter has a three-celled one, showing 

 that this condition is no barrier to fertilisation. .More 

 than twelve distinct crosses between different species of 

 these two tjenera are on record, and many plants have 

 been raised, but so far all resolutely refuse to flower, 

 notwithstanding the many inducements that have been 

 put in their way, and many of them are now large 

 vigorous plants, long past the usual flowering age. One 

 plant of these crosses is recorded to have flowered in 

 the United .States, but as it flowered exactly the same as 

 the mother plant in genus, species and variety, one can- 

 not be quite sure that the cross was really eft'ected. 



Many of the remaining plants (the writer has several 

 in his collection) are distinctly intermediate in their 

 foliage and habit of growth, and clearly bear the stamp 



•of their recorded origin. 



Secondary and Tertiary Hylm'ds. 



Of the 800 distinct crosses mentioned in the foregoing, 

 some 270 are secondary hybrids, i.e. hybrids of the 

 second generation, one or both parents being a primary 

 hybrid ; while thirty are tertiary hybrids, /.(. hybrids of 

 the third generation, one of the parents, at least, being a 

 secondary hybrid. .So far no hybrid orchids are recorded 

 to have flowered beyond the third generation, but perhaps 

 it may not be premature to mention that unflowered 

 hybrids of the fourth generation are known to be in 

 existence. The writer has in his collection six hybrids of 

 the fourth generation, five years old, all raised from the 

 same capsule, and which contain in their pedigree five 

 distinct species and three distinct hybrids. So that in the 

 near future there will be ample material in this direction 

 at the disposal of the student of heredity ; with this 

 ■distinct advantage, that orchids being individually 

 valuable, their pedigree is carefully and systematically 

 recorded, which unfortunately is more than one can say 

 •of the great majority of garden hybrids. 



.■\ careful e.xamination of secondary hybrids, shows 

 them to be very different from primary hybrids in their 

 range of variation. .-Vs we have already seen, primary 

 hybrids are comparatively uniform in their characters ; so 

 much so that, as a rule, they arc quite distinct from their 

 parents. On the other hand, secondary hybrids have a 

 ■much wider range of variation, often approaching either 

 parent, and sometimes even reverting wholly to one or the 

 other. For instance, to take the simplest form of a 

 secondary hybrid, i.e. a hybrid crossed with one of its 

 parent species. We find that the offspring, as a rule, 

 are very variable, a few reverting to tlie parent species 

 and a few to the parent hybrid ; but the great majority 

 are intermediate forms approaching either parent, the 

 whole forming a series of links between one parent 

 and the other. In short, we find that secondary hybrids 

 have a far wider range of variation than have primary 

 hybrids. 



Natural Hylirids. 



The existence of natural hybrids was formerly thought 

 by some naturalists to be highly improbable, if not 

 actually impossible. ISut now, when absolute facsimiles 

 of supposed natural hybrids have been raised by hand in 

 gardens, from the same two species among which they 

 naturally grow, they can no longer be regarded as pious 

 speculations, but are indeed accomplished facts. The 

 number of proved natural hybrids in orchids alone is now 

 very considerable, with the result that many intermediate 

 and doubtful forms, hitherto classed as distinct species, 

 are now placed in their proper position as natural hybrids. 

 Mr. R. k Rolfe, of Kew, has done yeoman service in 

 reducing the chaos of natural hybrid orchids to some- 

 'Ihing like order. And so it has come to pass that artificial 



NO. 1521, VOL. 59] 



hybridisation, which it was« ■ supposed would lea 

 systematic botany into the direst confusion, by the iron 

 of fate, seems destined to be the only trustworthy mean 

 of saving systematic botany from its own confusion ; an 

 the systematist, however orthodo.x he may be, can ni 

 longer afford to ignore artificial hybrids. 



Fertility of Hybrids. 



The question of the fertility of hybrids is a highly 

 interesting one, and especially important to the student 

 of evolution ; .-ind I venture to think that recent e.xperi 

 nients in orchid hybridisation have added considerably 

 to our knowledge of the subject. 



One of the principal objections to Darwin's theory of 

 the origm of species was the supposed general sterility 

 of hybrids. 



Darwin fully appreciated this difficulty, and, after a 

 careful and most elaborate survey of the whole question 

 of hybridism, came to the following conclusions :— 

 " First crosses between forms sufl'iciently distinct to be 

 ranked as species, and their hybrids are very generally, 

 but not universally sterile. . . . The sterility is of all 

 degrees " (" Origin of Species," 6th ed., p. 262). .■Vgain : — 

 "The sterility of distinct species, when first united, and 

 that of their hybrid offspring, graduates by an almost 

 infinite number of steps from zero (when the ovule is 

 never impregnated, and a seed capsule is never formed: 

 up to complete fertility. . . . This high degree of fertility 

 is, however, rare ("Animals and Plants,' 2nd ed., vol. ii. 

 p. 163). -Some fifteen years later. Dr. .-\lfred Kussel 

 Wallace took up a somewhat similar but more definite 

 position. He writes: — "One of the greatest, perhaps 

 we may say the greatest, of all the difficulties in the way 

 of accepting the theory of natural selection as a complete 

 explanation of the origin of species, has been the re- 

 markable difference between varieties and species in 

 respect of fertility when crossed. Generally speaking, 

 it may be said that the varieties of any one species, 

 however different they may be in external appearance, 

 are perfectly fertile when crossed, and their mongrel 

 offspring are ec|ually fertile when bred among thein* 

 selves ; while distinct species, on the other hand, ho\n 

 ever closely they may resemble each other externallw 

 are usually infertile when crossed, and their hybrifl 

 offspring absolutely sterile" ("Darwinism," 1890, p. 152J 

 Since that time, hundreds of hybrid orchids have been 

 raised in gardens ; as we have already seen, there are 

 now on record some 500 distinct i)rimary hybrids raised 

 from distinct species, also some 300 secondary and 

 tertiary hybrids from distinct crosses, raised froB 

 parents themselves hybrids. 



In the face of these facts, therefore, we can hardl; 

 maintain that "distinct species . . . are usually il 

 fertile when crossed," and still less can we assei 

 that " their hybrid offspring are absolutely sterile, 

 As it is with orchids, so it is with other garde 

 plants that have been hybridised, e.g. roses, rhod( 

 dendrons, dahli.is, chrysanthemums, carnations, b« 

 gonias, pansies, &c. : the wonderful forms seen 

 gardens at the present day are all hybrids of man 

 generations, being the known product of more tharT 

 one species ; and these are all fertile in the pro- 

 duction of seeds Darwin seemed to attach much 

 importance to the different degrees of fertility in hybrids 

 ranging from complete fertility down to absolute sterility. 

 \\ present we have no means of ascertaining the relative 

 fertility of hybrid orchids with that of ordinary species, 

 owing partly to the fact that very few crosses have been 

 made in gardens between varieties of the same species, 

 and partly to the fact that many thousands of seeds are 

 contained in one capsule, being practically innumerable. 

 But through the kindness of .Mr. Reginald Young, of 

 Liverpool -an enthusiastic connoisseur in Cypripediums 

 — the writer has been able to work out certain statistics 



