3-24 



NATURAL HISTORY OF PLANTS. 



. 160. Triflorous male 

 Auriferous scale. 



Fig. 161. Male floviferous 

 scale, flowers removed. 



number, are superposed to them. Barely the flower is 10—1.0- 



merous and 1 0-1 2-androus. 1 

 Ainuscordifoii j n t ] ie f ema i catkin, ordi- 



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 gynEecium is similar 

 to that of the Birches, and 

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

 membranous wing. The axillant scales there become woody. The 



Alders are trees and shrubs of the 

 Ahma giutiuosa. temperate and cold regions of both 



fifiÊffifi worlds in the northern hemisphere, 



rare in South America and south- 

 ern Africa. Their organs of vege- 

 tation are analogous to those of the 

 Birches. The leaves are accom- 

 panied by lateral stipules. The 

 flowei's are sometimes developed at 

 the same time as the leaves, but 

 more frequently earlier, and in this 

 case the females maj T , as in the 

 species constituting the genus 

 Jlnaster,- 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.* 



Fig. 165. Side view of 

 male floriferous scale. 



Fig. 166. Male flower. Fi 



167. Compound 

 fruit. 



1 In A. nitida Endl. and tiepaleusis Don, 

 of which has been made the genus Oletkropm 

 (Spach, .4m». Se. Nat. sér. 2, xv. 183, 201). 



- Spach, Ami. Sc. Nat. sér. 2, xv. 200 ; Suit, 

 à Biiffon, xi. 244. 



3 On these grounds Regel divides the 

 genus into 4 sections: 1. Clethropsis (Spach). 

 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 huds. Scales 3-florous. Fruit with 

 membranous wing. — 3. Phyllothyrsim (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 (Bct/ifa).— G.*:rtn. Fruct. ii. 

 54, t. 90 (Betula).— Lamk. Diet. i. 454 (Betula). 

 —Ait. Sort. Kcw. iii. 139 (Betula). — Ehrh. 

 Bcitr. 72 [Bit ula). — Mirb. Mém. Mus. xiv. 404, 

 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. Mém. Pé- 

 ttr*b. sér 6, ii. 162. — Ntjtt. Si/lv. Amer. Suppl. 

 i. 34, t. 10. — Ten. Ft. Nap. Prodr. 54; Icon.il. 

 340, t. 99.— Dcne. Ami. Sc. Nat. sér. 2, iv. 348. 

 — Sieii. et ZncC. Ahh, Akad. Munch, iv. Abtli. 



