224 



NATURAL HISTORY OF PLANTS. 



Fig. 160. Triflorous male 

 floriferous scale. 



Fig. 161. Male floriferous 

 scale, flowers removed. 



number, are superposed to them. Earely the flower is 10-12- 



merous and 10-1 2-androus.^ 

 Ahmscordifoiia. j^ ^j^^ female catkin, ordi- 



%: fifl. *. MK narily shorter, more rigid 



than in the Birches ^ and 

 erect, there are only two 

 flowers in the axil of each 

 of the thick scales, the 

 middle one being abortive. 

 The gynsecium is similar 

 to that of the Bh^ches^ and 

 the fruit, dry and monospermous, is wingless or surrounded by a 

 membranous wing. The axillant scales there become woody. The 



Aider's are trees and shrubs of the 

 Ainus giutinosa. temperate and cold regions of both 



worlds in the northern hemisphere, 

 rare in South America and south- 

 ern Africa. Their organs of vege- 

 .,.»««««^ tation are analosrous to those of the 



Fig. 165. Side view of ^^^S> -n- i rrn i 



male floriferous scale. ^^^K BiTches. lue Icaves are accom- 



panied by lateral stipules. The 



flowers are sometimes developed at 



the same time as the leaves, but 



more frequently earlier, and in this 



case the females may, as in the 



species constituting the genus 



Alnaster,^ emerge from buds bearing one or more leaves. Often the 



catkins are solitary, more rarely they are collected in clusters. 



About fifteen species of Alder are enumerated.* 



Fiff. 166. Mdle flower. 



Fig. 167. Compound 

 fruit. 



^ In A. nitida Endl. and nepalensis Don, 

 of which, has been made the genus Clethropsis 

 (Spach, Ann. Sc. Nat. ser. 2, xv. 183, 201). 



2 Spach, Ann. Sc. Nat. ser. 2, xv. 200 ; Suit. 

 a Sufon, xi. 244. 



3 On these grounds Kegel divides the 

 genus into 4 sections: 1. Clethropsis {Sfack). 

 Flowers developed at same time as leaves. 

 Male scales uniflorous. Female flower 10-12- 

 merous. — 2. Alnaster (Endl.). Flowers pre- 

 cocious. Male catkins coming from 1-3-phyl- 

 lous buds. Scales 3-florous. Fruit with 

 membranous wing. — 3. PhyUothyrsiis (Spach). 

 Flowers developed at same time as leaves. 

 Scales 3-florous. Floral buds aphyllous. Fruit 



with membranous wing. — 4. Gymnothyrsus 

 (Spach). Flowers precocious. Scales 3-florous. 

 Floral buds leafless. Fruit wingless or with 

 coriaceous wing. 



4 L. Spec. 1314 {Betuln).—QcKKi-if. Fruct. ii. 

 54, t. 90 {Betula).—LA.UYi. Diet. i. 454 (Betula). 

 —Ait. Hort. Few. iii. 139 {£ctttla).—EKB.H. 

 Bcitr. 72 {Betula). — Mirb. Mem. Mus. xiv. 464, 

 t. 22.— W. Spec. iv. 334.— H. B. K. Nov. Gen. 

 et Spec. ii. 16.— DC. Fl. Franc, iii. 304.— 

 Don, Prodr. Fl. Nepal. 58.— Bong. Mem. Pe- 

 tersb. ser 6, ii. 162. — Nutt. Sylv. Amer. Suppl. 

 i. 34, t. 10.— Ten. Fl. Nap. Prodr. 54 ; Icon. ii. 

 340, t. 99.— DcNE. Ann. Sc. Nat. ser. 2, iv. 348. 

 — SiEB. et Zucc. Abh. Akad. Miineh. iv. Abth. 



