1921] SCHNEIDER, NOTES ON AMERICAN WILLOWS, XII. 115 



plusminusve dense subdistincte glanduloso- serrato-denticulata; 

 petioli undique tomentelli; species rara mexicana . 8. S. jaliscana. 

 Folia lanceolata vel oblongo-lanceolata, basi cuneata vel obtusa, 

 apice acuta vel sensim breviter acuminata, 5.5: 1.7 ad 10:2.7 cm. 

 magna, indistincte crenato- vel undulato- dentata; petioli superne 



puberuli; species rara quebecensis 101. S. paraleuca. 



Petioli saltern foliorum ma jorum longiores vel stipulae ma j ores vel folia 

 latiora. 

 Folia tantum juvenilia pilosa, adulta papyracea, subtus satis laevia, 

 nervillis haud vel vix prominulis, elliptico-oblonga ad late elliptico- 

 lanceolata, basi obtusa ad rotunda, apice acuta vel subito et oblique 

 breviter acuminata, 7:3 ad 12:4-15:5 cm. magna, plusminusve ir- 

 regulariter subundulato-denticulata; ramuli glaberrimi; petioli 10- 

 20 mm. longi (confer etiam formas glabras 95. S. discoloris foliis 



subtus saepissime evidentius reticulatis) 79. S. Piperi. 



Folia pleraque etiam adulta plusminusve pilosa, textura crassiore vel 

 subtus evidentius reticulata vel magis lanceolata vel oblanceolata. 

 Confer 95. S. discolorem et 96. S. Scoulerianam. 

 Pubescentia nunquam pilis fulvis mixta, saepe etiam foliorum novellorum 

 nulla (in S. coactili interdum pubescentia partim fulva adest). 

 Folia novella pellucida, balsamifera, citissime glaberrima, late ovata, 

 elliptica vel elliptico-oblonga, bayi pleraque rotundata vel subcordata, 

 apice obtusa ad subacuminata, subtus conspicue reticulata, margine 

 dense crenato-serrata vel crenata, 2.5-3:1.5-1.8 ad 7:3 vel 10.5 :3.5 

 vel 9:5 cm. magna; petioli (5-) 8-25 mm. longi; stipulae nullae vel 

 minimae; ramuli glabri, castanei, nitiduli . . . . 72. S. pyrifolia. 

 Folia novella haud balsamifera vel aliis signis diversa (confer etiam 

 species mihi nonsatis cognitae 73. S. obtusatam et 88. S. prolixam). 

 Laminae apice plusminusve breviter acuminatae, 1 maximae saepis- 

 sime ultra 7-9 cm. longae, ovato-vel elliptico-lanceolatae vel el- 

 liptico-oblongae, fere semper infra medium latissimae. 

 Ramuli annotini biennesque lutescentes vel flavescentes, partim 

 rubescentes; folia ovato-oblonga, elliptico-lanceolata vel lanceo- 

 lata, subintegra vel plusminusve obscure, rarius distinctius densius 

 que glanduloso-serrata, superne satis flavescenti-viridia, ad 10-13.5: 

 2-3.5(-6) cm. magna; stipulae saepissime lunatae vel subreni- 



formes, intus basi glandulosae 60. S. httea. 



Ramuli annotini biennesque plusminusve fuscescentes, purpuras- 

 centes, castanei vel sordide brunnescentes. 

 Folia margine plusminusve irregulariter conspicue et argute 

 lobulato-dentata dentibus patentibus ad 2 mm. longis, oblonga 

 vel elliptico-lanceolata, 7:2 ad 1 1(— 15) : 2.5-3(-4) cm. magna, 

 subtus initio dense sericeo-pubescentia, matura satis glabres- 

 centia; stipulae lanceolatae, acuminatae, ad 8 mm. longae (spe- 

 cies rara ex Maine) 91. aS. coactilis. 



Folia breviter serrata vel crenato-dentata vel subintegra et sig- 

 nis aliis diversa. 

 Pagina superior foliorum vivide viridis et plusminusve nitida; 

 folia ab initio glaberrima vel novella superne tantum in 

 costa pilosa. 

 Stipulae (in surculis exceptae) nullae vel narvae, lanceo- 

 latae ad subreniformes, petiolis 2- ad pluriplo breviores; 

 folia etiam matura subchartacea, ovato- vel elliptico-lanceo- 

 lata, interdum obovato-lanceolata, basi cuneata ad cordata, 

 7:1.5-2.5 ad 14:6.3 cm. magna, plusminusve breviter ser- 

 rata vel serrato-denticulata . . . 59. S. mackenzicana. 

 Stipulae distinctae, late semicordatae, ad 13:8 mm. magnae; 

 folia chartacea, ovata vel ovato-elliptica, basi rotundata ad 



1 It is an extremely difficult task to characterize the differences of the leaves of the 

 following species without the help of a series cf good illustrations. I do not pretend 

 to give more than a few hints which may lead other students to the elaboration of a 

 more useful key. 



