462 WILSON EXPEDITION TO CHINA 



CONSPECTUS ANALYTICUS BETULARUM ASIAE ORIENTALIS 

 NEC NON HIMALAYAS. 



Amenta fructifera ad 2-4 racemoso-conferta v. solitaria, pendula, longe et anguste 

 cylindrica; lobi laterales bractearum valde reducti v. in B. Maxim oivicziana 

 tant um distinctiores ; samararum alae latae, bracteas lateraliter superantes v. 

 nuculis fere triplo latiores. Folia multi(9-13)-costata. 



Sect. I. ACUMINATAE 



* Amenta fructifera ad 2-4 racemoso-conferta (rarius interdum abortu solitaria) 



Lobi laterales bractearum distinct!, medio circiter dimidio breviores; sa- 

 mararum alae nuculo fere triplo latiores. Folia magna, late ovata, basi 

 profunde cordata; petioli 2.5-4 cm. longi . . . .1. B. Maximovicziana 

 Lobi laterales bractearum reducti. Folia ovato-oblonga v. basi baud cor 

 data; petioli 1.2-2(-2.2) cm. longi. 

 Ramuli hornotini petioliijue distincte flavo- v. griseo-tomentelli et etiam 

 pedunculi et saepissime costa paginae inferioris foliorum eodem tomento 

 obtecta. Folia late ovata v. ovato-oblonga, basi rotunda v. leviter 

 cordata, satis subito acuminata, dentibus plus minusve distantibus. 



2. B. cylindrostachya. 



Ramuli hornotini petiolique breviter pubescentes v. pleraque tantum 



pilosi V. subglabri, saepe glanduliferi (pedunculi tantum saepe distinctius 



tomentelli). Folia ovato-oblonga, sensim acuminata saepe caudata, 



basi rotundato-truncata v. subacuta, dentibus plus minusve adpressis. 



3. B. alnoides. 

 ** Amenta fructifera solitaria; lobi laterales bractearum reducti. 



Petioli 0.8-2.5 cm. longi. Amenta fructifera 3.5-11 cm. longa; bractearum 

 lobus medius elongatus lateralibus parvis v. minimis valde longior. Folia 



pleraque plus quam 6 cm. longa 4. .B. luminifera. 



Petioli 6-8 mm. longi. Amenta fructifera 3-4 cm. longa; bractearum lobus 

 medius satis brevis. Folia tantum 5-6 cm. longa . . . 5. B. Baeumkeri. 



Amenta fructifera solitaria (rarissime bina) pendula, patentia v. erecta; lobi 

 laterales bractearum distincti ; samararum alae niicula vix latiores, saepe an- 

 gustissimae; bracteae samaras occultantes. 



* Amenta fructifera erecta, pleraque subglobosa, ovata v. anguste elliptica (in 



10. B. Schmidtii cylindrica); bractearum lobi laterales fere semper erectae 

 V. erecto-patentes medio distincte producto plus minusve breviores. Folia 

 nervis lateralibus supra plus minusve impressis (6-)7-14 instructa. (Confer 



etiam 25. B. davuricam) Sect. 2. COSTATAE. 



t Samararum alae satis distinctae, nucula circiter }/2, rarius ad ^ angustiores; 

 amenta fructifera ovato-cylindrica v. subc.ylindrica, 2-3-plo longiora 

 quam lata, pedunculo satis distincto et tenui suffulta (v. folia triangu- 

 laria versus basim latissima; vide 6. 5. Ermanii). 



Subsect. a. Ermanianae. 

 Folia plus minusve triangularia v. ovato-triangularia, versus basim latis- 

 sima, basi truncata, plus minusve cordata v. rarius subrotunda. 



6. B. Ermanii. 



Folia ovata, ovato-oblonga v. ovato-rotunda, medio v. versus medium 



(rarius supra medium) latissima, basi saepissime rotunda v. subacuta, 



interdum cordata. 



Nervi laterales foliorum majorum utrinque 6-9. . 7. B. Jacquemonlii. 



Nervi laterales foliorum (9-) 10-14. 



