PROPAGATION. 



329 



Welfia. — The name is a transformation from 

 " Guelph," and the genus includes a few small- 

 growing and extremely handsome plants ; they are 

 useful for table decoration in a very young state, and 

 are beautiful ornaments at any time. 



W. Greorgil— stem slender, 

 destitute of spiues ; leaves 

 piimate ; leaflets sessile. 

 CostA Kica. 



W. xegia — ^tjiis is a more 

 slender species ; whole 

 plant smootii, bearing 

 long, pinnate, arcliing 



leaves, with pendent leaf- 

 lets; when young the 

 entire leaf and petiole 

 is rich, bright crimson, 

 which gradually fades 

 away to bright, shining 

 green. New Grenada. 



PEOPAGATION. 



THE FORMATION OF VARIETIES. 

 Bt John Fsasee. 



THE phenomena of fertilisation, the construction 

 of flowers, and their adaptation to the require- 

 ments of insects, have been treated of under the 

 head of Fertilisation, Vol. III., pp. 187-192. 



To provide for the accomplishment of this act, 

 nature furnishes many and varied means, a few of 

 which have already been mentioned. Having learned 

 the importance of fertilisation, and knowing also 

 that our improved fruits, flpwers, and vegetables 

 have been remoulded from the parent wildings, to 

 please the fancy or meet the necessities of man, we 

 are all the more encouraged to enter this wide field of 

 labour, where there is unlimited scope for our abilities, 

 and plastic nature, so to speak, is in our hands. 



Nature herself brings about changes and improve- 

 ments ; but some of her handiworks have taken ages 

 for their accompEshment, whereas man, on scientific 

 principles, and by careful intelligent working, can 

 bring about marvellous results in a comparatively 

 short time. Furthermore, natural productions are 

 fitted to compete with other plants, and perpetuate 

 their existence, in that part of the world where 

 created. On the other hand, artificially created 

 plants, or those produced by the agency of man, 

 require his assistance for their propagation, dissemi- 

 nation, and preservation, in proportion to the extent 

 they difier from the original wilding. 



As the chief aim of the gardener and hybridist is 

 to improve existing varieties, or produce new forms, 

 this wide subject may be considered imder the fol- 

 lowing three headings : — 



I. Hybridisation, or the crossing of species and 

 genera. 



II. The intercrossing of varieties. 



III. Selection. 



I. Hybridisation. — The art of hybridisation, 

 when applied to the intercrossing of species or even 



genera, is not only more fascinating, but opens up a 

 far wider field of unexplored territory, and requires 

 even more intelligence to conduct it properly, than 

 the mere crossing of varieties. The difference, 

 however, between species and varieties is merely 

 one of degree, and quite arbitrary, made to suit the 

 convenience of botanists. This was recognised at 

 least as early as the days of Herbert, whose leading 

 idea, nevertheless, was that every species that would 

 hybridise with another should be included in the 

 same genus. But we have now authentic records of 

 numerous bigeneric hybrids, and on the other hand, 

 find that in some instances it is as difficult to hy- 

 bridise varieties as it is good recognised species. 

 This is notably the case in dimorphic and trimorphic 

 flowers of the same species, the latter represented Ly 

 Lythrum Salicaria, and the former by JPrimula, as 

 well as others to the number of forty genera scat- 

 tered through various natural orders. 



Granted that we keep within a certain degree of 

 systematic relationship, the other obstructions 

 that bar the way to freedom of intercrossing, and 

 fertility of the offspring, are chiefly to be found in 

 difierences affecting the reproductive elements, and 

 the changes they have undergone during many suc- 

 cessive generations, while acting independently of 

 one another. For instance, of two species with 

 pollen very different in size, the poUen-tubes of the 

 smaller grains would be able to penetrate the larger- 

 canaUed style, while the hybridist would be unable to 

 obtain a reciprocal cross from the same two species, 

 by reason of the larger poUen-grains being unable 

 to penetrate the narrow passages of the style. The 

 different lengths of style will also offer obstacles 

 to the pollen in attempting to reach the ovule. 



In the case of the Strawberry, Fragm-ia, the flowers 

 are polygamous-dioecious, either functionally or 

 morphologically, or both, and proterogynous, that 

 is, the pistil matures first. This is a great assist- 

 ance to the hybridist, enabling biTn to remove the 

 stamens before shedding their poUen. Fragaria 

 vesca presents serious difficulties in forming a union 

 either with Hautbois or the American species. Such 

 a stock would be desirable, because thoroughly 

 inured to our climate. Hautbois is generally uni- 

 sexual, and supposed to have originated from J^. 

 iiesca. To be able to infuse its peculiar and agree- 

 able flavour into a stock worth cultivatiug would be 

 an acquisition. "Williams, of Pitmaston, succeeded 

 in effecting the first cross, but the fruit of the 

 resulting progeny was almost invariably seedless, a 

 notable instance of the pollen affecting the fleshy 

 receptacle, and yet lacking the physiological poten- 

 tiality of producing an embryo. F. Tirginiana, 

 CMliensis, and grandijiora, belonging to widely 

 separated parts of America, intercross with the 



