GS JOFRXAL OF THE ARNOLD ARBORETUM [vol. i 



Tlic following key is mainly based on ilie cliaractcrs afforded by tlie 

 leaves. I liave not yet been able to elaborate separate keys for male and 

 female s])eciniens of which the determination is a ratlier <limnilt task owing 

 to the precoelousness of the aments and the great similarity especially of 

 the male flowers. It needs a carefnl comparison of a well-collected series of 

 flowering specimens of each species to thoroughly cstabhsh the differences 

 between them without the aid of the leaves. 



CLAVIS SPECIERL M VARIETATU.MQTT. 



Folia nonualia superiora adulta glabra vel fere glabra (confer etiam Gb. .9. pdli'tam 



var. jisilam); ramuli lioniotini aunotiiuque plus nn"nusve castanci vol purj>ureo- 



bninnci ot nitidull sed hand vol raro Icviter pruinosi. 



Stipulae fore seni})er valde cvohitae, Iinoaros ud laiioeolatao. donticulatac, sacpe 



porsistontos, 0,5-2.5:0.1-0.6 cm. magnae; folia suporiora phis miiiiisve 



rhombico-obluucoolata, obovato-obloii^a vol r]iombioo-ollii)tioa, utrinque 



acuta vol apice foro subacununata, -1:1.5 ad 6:2.5 vol surculorum ad 10:3.2 



cm. magna, margiuc intogerrima vol satis indistiiioto rarius subdensitis glandu- 



loso-sul)sorrata, suporne intense viridia, saoi>issimo ostomatifora, subtus 



albo-glaurescontia; petioli 5-10 mm. longi; amonla mascula oiroiter 2.5-3.5:1.2 



cm., fruotifera ad 6.5 cm. magna; fruotus ovuidoo-rostrali podicollo brovissimo 



glandula ^- ad 2-pl() brevioro cxcluso 7-8 mm. magni; styli 1.2-2 inm. longi. 



Rannili novelli glabri vol sparse (interdum etiam annotini parce unilateral iter) 



1*''**-^' 1. S.jndchra. 



Kaimih novolli dense gnsoo- vol flavcsccnti-villoso-toniontosi. 



lb. S. pulchra var. yiil'onensis. 

 Stipulao semper nullao vol etiam in ramulis vegotis quam petioli duplo brevloros, 

 (bviduac ot planta(^ aliis signis divorsae. 

 Filamenta basi pilosula; folia superiora ramulonnn brevionmi vol (iufima et) 

 media ramnloruni vegotorum angusto ad late ol^ovata vol obovato-oblonga, 

 basi plusminusvc runeata, apice subito brovissime acuta vol plioato-aouta! 

 4:1.8 — 0:3.3 vol ad 7,5:3 vol angnstioraad (J:2oni. magna, initio subtus plus 

 minusvebrovitorsorlcoo-pilosa; amenta feminea 4.5-0.5 (-8) em. magna; fruc- 

 tus ellipsoidei subrostrati, ad 8 mm. longi podicollo ad 1.5 mm. longo cxcluso. 



5. S. pennafa. 

 iMlamonta glaborrima; folia haud vol rarissimo late obovalia et plautao aliis 

 sigiiis diversae. 



Fructus perfoote maturi 5-0 mm. longi podicollo brovi glandulam baud vol 

 vix i-pio superante excluso; styli 0.8-1.5 mm. longi; amonta fruotifera vix 

 ulti;a 4:1.2 cm. magna, mascula 1-2:1-1.2 cm. magna; folia (surculorum 

 ex parte excepta) intogerrima vol (ploracpie tantum parlim) satis indis- 

 tinoto glanduloso-oronato-dontieulata, lanceolata. olliptico-Ianccolata, el- 

 hptioa vol obovato-ol)longa, utrinque acuta vol apioo obtusiora, rarius 

 ovali-Ianoeolata. 2:0.7 ad ploracjuo haud ultra 5:2-1.5 cm. magna, suporne 

 vivido viridia, (novella saepe excepta) glaborrima, ostomatifora vol stomati- 

 bus i)lusminusve numorosis praodita, subtus valde disoolorla, glaucoseentia, 

 glabra vol sparse brevitor pilosa (confer otiani .S'. Nelsonil, p. 80). 



4. S. planifolia ot var, 

 Fruotus perfeote maturi 7-10 mm, longi podicollo glandulam 2- vol pluriplo 

 superante exeepto ot plantae aliis signis divorsae. 

 Folia normalia i^lus minusve distinctc (interdum tantum parlim) cronato- 

 vel dontato-serrata, adulta subrigido chartacea, 4:1.5 ad 8:3 cm. magna, 

 superne glaborrima vel initio ad costam puborula, demuin lucido viridia,' 

 subtus glaucesoontia, glaborrima vol novella sparse (pilis intordum rufis) 



