Amentales.] 



BETULACE^. 



251 



Order LXXVIII. BETULACEiE.— Birchworts. 



Amentaceae, Juss. Gen. 407. (17S9) in part.— Betulinese, L. C. Richard in A. Richard, Elan. Bot., ed. i., 

 5G2. (18-28.)— BetiUacese, Bartl. Ord. Nat. 99. (1830) j Endl. Gen. Ixxxviii. ; 3Ieisner, p. 351. 



Diagnosis. — Amental Exogcns, xcitli a 2-celled ovary, a solitary pendulous ovule, and a 



superior radicle. 



Trees or shnibs. Leaves alternate, simple, with the primary vems often runnmg 

 straight from the midrib to the margin ; stipules deciduous. Flowers $ ^ , amenta- 

 ceous, with small 

 scales for their 

 calyx, which are 

 sometimes arranged 

 in a whorl so as to 

 simulate a real calyx 

 (Ahius). $ Sta- 

 mens distinct, oppo- 

 site the calycine 

 scales ; anthers 2- 

 ceUed. $ Ovary 

 free, 2-celled; o- 

 vules solitary, pen- 

 dulous, auatropal ; 

 style single, or none ; 

 stigmas 2. Fruit 

 thin, indehiscent, by 

 abortion 1 -celled, combined with 

 the scales into a sort of cone. Seeds 

 pendulous ; albumen none ; em- 

 bryo straight ; cotyledons flat ; 

 radicle superior. 

 The various kinds of Birch and Alder alone make up this Order, 

 which is distmctly defined, among the Amental AlUance, by its 

 fiiiit consisting of two carpels, in each of which there is but one 

 pendulous o^•ule. If they had albumen, they might be regarded 

 as Urticaceous plants with pendulous seeds and double carpels. 

 Their nearest approach to other Orders is to Liquidambai's, which 

 have a little albumen, and numerous amphitropal o\-ules. In the 

 male flowers of several species there is a distinct approach to the 

 formation of a fom'-leaved membranous calyx. The leaves have 

 the same venation as iMastworts, which, however, have an adher- 

 ent calyx, and thus are distinguished by a well-marked character, 

 independently of theu* cupule or involucre. 



Irdiabitants of the woods of Europe, Northern Asia, the Hima- 

 layas, and North America, and even making then- appearance on 

 the mountains of Peru and Columbia, and in the antarctic regions, 

 of existing up to the last limits between land and eternal snow. 



The species are usually timber trees, with deciduous lea\'«s ; theu' bark is astringent, and 

 sometimes employed as a febrifuge ; but they are chiefly valued for their importance as 

 ornaments of a landscape. Their wood is often light, and of inferior quality, but that 

 of the Black Bu*ch of North America is one of the hardest and most valuable we know. 

 The bark of tliis species has a singular acrid taste ; it contains a balsamic oil, and a peculiar 

 resinous substance called Betuline, or Birch Camphor. The oil extracted from the Com- 

 mon Birch is employed in dressing Russia leather, and gives it its well known smell. 

 From Betula papjTacea the North American Indians strip off" the thick tough bark, and 

 manufactiu'e it into boats, shoe-soles, and various domestic utensils. The sap of the Com- 

 mon Birch (B. alba) is obtained in the spring by tapping the trees, and, on account of 



Fiff. CLXVIII. 



Fig. CLXIX. 

 They appear capable 



Fig. CLXVIII.— ^ and ^ catkins of Betula alba. 

 Fig. CLXIX.— Betula lenta. 1. ^ flowers ; 2. ^ flowers 

 4. transverse section of it. 



3. perpendicular section of a ripe fruit ; 



