SALICACEAE. — POPULUS 27 



* Folia subtds distincte (in vivo) discoloria, albescentia, turionum et ramulorum 

 inter se pleraque satis dimorpha; ^ petioli basi tereti, apice vix v. non 

 compressi supra canaliculati; gemmae satis viscosae, balsamicae. Brac- 

 teae florum valde fimbriatae sed non v. vix ciliatae. 



Sect. 3. TACAMAHACA. 

 Flores feminei fructusque distincte pedicellati, florum masculorum antherae 

 3-33^-plo longiorae quam latae. Turiones [teste Hooker et Dode] angu- 

 latae. Folia turionum ramulorumque diversorum, ut videtur, haud valde 

 dissimilia, nunc ovato-acuminata, basi rotunda v. cordata v. raro sub- 

 truncata, in specim. visis 7:4.5-17:12 cm. magna, nunc late ovato- 

 cordata, brevius acuminata v. acuta, c. 8:8-15:12 cm. magna, omnia longe 

 petiolata, pedicellis subteretis, glabris v. versus apicem sparse puberulis, 

 3-12 cm. longis, crenato-glanduloso-dentata, fere semper distincte ciliata, 

 supra intense v. claro-viridia, subtus albescentia, utrinque (an semper?) 

 glabra. Amenta glabra, mascula ad 10 cm. longa, fructifera ad 30 cm. 

 longa, fructibus satis distantibus, glabris, ovato-globosis, in apicem pro- 



ductis 6. P. ciliata. 



Flores feminei fructusque sessiles v. subsessiles; antherae (a me visae) 

 vix plus quam duplo longiores quam latae. 

 Ramuli juveniles cylindrici, interdum apice ut turiones angulati v. 

 striati, biennes semper teretes (confer etiam 9. P. szechuanicam, var. 

 tibeticam). 



Ramuli initio olivacei vix v. non brunnescentes, deinde flavescentes v. 

 ochroleuci, glabri v. supra nodos versus gemmas puberuli. Folia 

 membranacea v. papyxacea, supra plus minusve intense viridia, subni- 

 tentia et vix opaca, glabra v. basim versus sparse pilosa, subtus dis- 

 coloria, opaca, albescentia v. in sicco flavescentia, glabra (sed vide 

 ya,T. macrocarpam ut p. 19 indicata!); margine glanduloso-crenulata, 



* It is helpful to keep the follovfdng in mind in regard to the variability of the 

 leaves of Populus (of this section and also of the others). L. A. Dode was the first 

 who clearly described the variation of the leaves according to the age of the plants, 

 the position of the branches, and the chmatic and other conditions under which they 

 were produced. He distinguishes many different kinds of shoots (pousses) and of 

 leaves. Unfortunately Dode's descriptions in his "Extraits" are so incomplete 

 that it is impossible to form an opinion of the real value of all his different species. 



I think it sufficient if we distinguish 3 different kinds of leaves: 1. the leaves of 

 the offshoots or suckers (folia turionum radicalium); 2. the leaves of the normal 

 but not the vigorous shoots of the young plants (foha ramorum [sed non turionum] 

 plantae juvenilis); and 3. the leaves of the old trees (folia arboris adultae fructi- 

 f erae) . The leaves of the third kind we usually find at the ends of vigorous branches 

 of young plants when they are growing well and becoming mature. If we compare 

 leaves of different species it is necessary to be very careful only to compare the 

 same kind of leaves! 



Referring to the pubescence of branchlets, leaves and petioles, many of the species 

 of Populus seem to produce a glabrous and a pubescent variety, both closelj' con- 

 nected by intermediate forms, but sometimes quite distinct in the extreme forms. 



There is another character in Populus which seems to be very often overesti- 

 mated, that is whether the young shoots are angular or cyUndric. As far as my 

 observations go vigorous shoots (and offshoots) of nearly every species with cylin- 

 drical branchlets may be more or less angular, at least at their apex or when the 

 branch is very young. 



