456 



SALIcfNE.^ 



common. Possibly a hybrid between the preceding and the 

 following species. — Fl. March, April. Perennial. 



3. P. tremula (Aspen). — A tree with grey bark ; many downy 

 suckers ; spreading branches ; downy buds and shoots ; leaves 

 nearly round, acute, cordate, serrate, glabrous on both surfaces, 

 or downy when young ; stigmas 2, 2-fid, erect. — Woods ; common. 

 — Fl. March, April. Perennial. 



4.* P. nigra (Black Poplar). — A large tree with grey bark; 



no suckers; spreading 

 branches ; sticky buds ; 

 glabrous shoots ; rhom- 

 boid, acuminate, serrate, 

 cuneate leaves, glabrous 

 on both surfaces, silky 

 beneath when young ; 

 stamens 12 — 20; anthers 

 red ; stigmas 2, roundish, 

 2-fid. — River-banks ; not 

 indigenous. — Fl. March, 

 April. Perennial. 



Among introduced 

 forms now largely grown 

 are P. delioidea, the 

 American Black Poplar, 

 with leaves truncate at 

 base and with ciliate 

 margin; and P. seroiina, 

 the Black Italian Poplar, 

 a very quick-growing 

 form, with straight stem 

 and ascending branches, 

 a cross between P. nigra 

 and P. deltoidea. 



POPULUS TREMULA (As/en). 



Class II. MONOCOTYLEDONS 



In the plants belonging to this class the embryo of the seed has 

 only a single cotyledon or seed-leaf. Though in their earlier stages 

 Palms develop a radicle or tap-root, no British representatives of 

 the Class do so ; nor, with the one exception of the Butcher's 

 Broom [Ruscus aculedtus), do they form woody stems. They 

 have generally bunches of fibrous roots ; their stems are often 

 bulbs or corms, and are not commonly much branched. Internally 

 there is no distinct pith, separable bark, or annual rings of wood 



