COMBINATION' OF PARKNT-CHARACTERS. 563 



corresponding structure in Centaurea Scabiosa is bordered by a broad, membranous, 

 fringe-like edge of a dark-brown colour. In Centaurea sordida (Grafiava), 

 the hybrid offspring of these two species, each involucral leaf is edged with a 

 narrow, light-brown membranous and fringed border, and terminates in a short 

 yellowish prickle. A very instructive example of the union of parental characters 

 aflecting all the different parts of the floral region is afforded also by the Labiate 

 Marruhium remotum, which is produced by crossing Marrubium peregrinum and 

 M. vulgare. The small tuft-like inflorescences in the leaf-axils of Marrubium 

 peregrinum include from 10 to 18 flowers, those of M. vulgare from 4 to 5, and 

 those of the hybrid M. remotum from 5 to 10. The calyx of M. peregrinum is 

 grey and covered with felted hairs, and its margin is provided with five large 

 subulate teeth which terminate in straight points. The calyx of M. vulgare is 

 green and sparsely clothed with hairs, and its edge has ten small teeth which 

 terminate in stift' reflexed points like hooks. Five of these teeth are rather longer 

 than the rest. The calyx of M. remotum is greyish -green and clothed with a 

 loose felt; its edge is furnished with five big subulate teeth which terminate in 

 stiff out-curved points, and have from two to five very small teeth interspersed 

 between them. The three lobes of the under-lip of the corolla are almost of equal 

 length in Marrubium peregrinum, whilst in M. vulgare the middle lobe is three 

 times as long as the two lateral lobes. In the hybrid Marrubium remotum, the 

 middle lobe of the lower lip is half as long again as the lateral lobes. An excellent 

 example is also afforded by Dianthus CEnipontanus, a hybrid Pink resulting from 

 a cross between Bianthus alpinus and B. superbus. In B. alpinus the bract-like 

 scales at the base of the calyx are almost as long as the tube of the calyx itself, 

 whilst in D. superbus their relative length is only a quarter or a third ; in the 

 hybrid B. CEnipontanus these bracts are half as long as the tube. The petals of 

 B. alpinus have broad laminse beset at the margin with short triangular teeth, 

 those of B. superbus have their laminaj slit up into a number of narrow strips, and 

 those of B. CEnipontanus have deeply-incised laminfe, the margins being divided 

 into linear segments. The dimensions of the various parts of the flower in a hybrid 

 also exhibit in most cases a combination of the corresponding parental character- 

 istics. Thus, for instance, the perianth of the Orchid Gymnadenia conopsea has a 

 long spur — that is to say, the segment of the perianth known as the labellum is 

 produced backwards into a saccate protuberance supposed to resemble a spur, and 

 this portion of the petal in Gymnadenia conopsea is 15 mm. in length. In Nigri- 

 tella nigra, on the other hand, the spur is very short, measuring about 2 mm. The 

 hybrid of these two Orchids, Nigritella suaveolens, has a spur varying from 5 to 

 7 mm. in length. In Willow hybrids the number of stamens in each flower of the 

 hybrid is invariably between the corresponding numbers in the two parent- 

 species. For example, the number of stamens in a flower of Salix alba is 2, in 

 Salix pentandra 5-12, and in their hybrid Salix Ehrhartiana 3-4. 



The cellular structures produced from the epidermis of the stem and leaves 

 which are differentiated as hairs, bristles, scales, glands, &c., and are classed together 



