ABIES. 487 



the epidermis of the under side ; and by their erect cones, the 

 scales of which soon fall off after the seed is mature leaving the 

 axis on the tree from which, however, it soon disappears. Botanically 

 the genus is thus distinguished : 



Inflorescence monoecious. Stamiuate flowers numerous, axillary on 

 branchlets of the preceding year, shortly stalked, cylindric or ovoid- 

 cylindric, and surrounded at the base by numerous involucral bracts. 

 Stamens spirally crowded around a central axis ; anthers shortly stipitate, 

 with a small knob- or spur-like projection, dehiscing transversely and 

 variously coloured. 



Ovuliferous flowers few, usually on the upper side of the higherniost 

 branches, globose or cylindric, erect, composed of numerous imbricated 

 scales spirally inserted on a central axis, each bearing near the base 

 on the ventral (inner) side, two inverted ovules. 



Cones cylindric, rarely ovoid, composed of thin, ligneous imbricated 

 scales, mostly of fan-like shape, in many series, each bearing on the 

 ventral face two seeds of which the testa or outer coat is prolonged 

 into a membraneous wing, and on the dorsal face a narrow mucronate 

 bract shorter or longer than the scale and adnate to it at the base. 



Fig. 124. Transverse section of leaf of Abies pectinate x 32 ; r, resin 

 canals ; /, tibro-vascular bundle. 



Twenty-four species of Abies or forms recognised as such are 

 described in the following pages, but some of them are connected by 

 intermediate forms that render the technical expression of specific 

 characters in such cases extremely difficult. Throughout the genus a 

 general uniformity in habit and structure prevails so that sectional 

 divisions of it are scarcely necessary. The greatest deviations from the 

 common type occur in three of the western North American species, 

 <ind taking these into account the late Dr. Engelmann proposed the 

 following sections.* 



EUABIES. Leaves flat, grooved above, stornatiferous sometimes on the 

 upper and sometimes on the lower surface. 



BRACTIEAT^:. Leaves flat without stomata on the upper surface (Abies 

 bracteata). 



XOBILES. Leaves flat or tetragonal, stomatiferous on both surfaces 

 (A. nobilis and A. magnifica). f 



* Transactions of the St. Louis Academy, Vol. Ill, p. 596. Gordon (Pinetum, ed. II. 

 p. 197) distributed the Silver Firs in two sections, placing in one those species in which 

 the bracts of the cone are longer than the scale and exserted, and in the other those in 

 which the bracts are shorter and enclosed ; a distinction that is quite futile as Beissner 

 lias pointed out, since the length of the bract is variable in the same species, being some- 

 times exserted, sometimes enclosed, as in -Abies balsamea, A. magnifica, A. Veitchii. 



f Besides the sectional character on whicli Engelmann has placed the greatest stress, 

 Abies bracteata differs from all the other species in its larger leaves, longer winter buds with 

 white perulffi, and especially in its ovoid cones with long bristle-like exserted bracts. 

 A. nobilis and A. magnifica differ from all other Abies in their large cones and bluish-green 

 crowded leaves. 



