ENGELMANN REVISION OF THE GENUS PINUS, ETC. I 73 



peculiarity of some species to retain their seeds in temporarily 

 or permanently closed cones, when they are called serotinous. 

 Such are southern forms of P. rigida (var. serotina) and P. inops 

 (var. clausa)^ rarely P. Tee da ; in some Californian {P. insigizis., 

 hiberczilata^muricata) and Mexican species {P.patula, Teocote 

 and Greggii) this is still more conspicuous. The seeds of such 

 serotinous cones seem to retain their germinating power for many 

 years longer than loose pine seeds, which are known soon to lose 

 their vitality.* 



The SEEDS are obovate, or often more or less obliquely trian- 

 gular, rarely (in P. Sabiniana and Gerardiaiid) nearly cylin- 

 drical, generally somewhat compressed, 3 to 12 lines in length, 

 smooth or often on the lower Surface ridged or slightly tubercu- 

 lated, alwaNS destitute of balsam vesicles, pale gray or yellow- 

 ish, or spotted, or brown, and often black. A wing is always 

 present, and is generally several times longer than the seed ; in 

 some large-seeded species (/^. Jlexilis^ Ce?ftbra, edulis and the 

 other nut-pines, and Pined) it is reduced to a narrow rim, which 

 is apt to remain attached to the scale when the seed is liberated ; 

 in P. parvijiora^ Bungeana^ Gerardiana, Torreyana^ and 

 Sabiniatta^ it is more conspicuous, but shorter than the seed 

 itself; in P. Coultei-i it is about as long as the seed, and in P. 

 Lambertiana longer. The size of the seed and the projoortion 

 of the wing to it has been considered to furnish valuable sec- 

 tional characters, but it proves to be only of specific importance. 

 The wing is always more or less oblique and widest in some 

 species upwards, in others near the base. The base of the wing 

 forms a rim which surrovmds the seed, leaving its under side free 

 and with its edge covering part of, or rarely the greater part {P. 

 Elliottii) or the entire upper side (only seen in P. Banksiand). 

 Generally the wing and its rim is completely separable from the 

 mature seed, but in a few species {^P. Strgbus and allies) it ad- 

 heres to it closely, and is at last broken off irregularly. 



The COTYLEDONS, 4 or 5 to 15 or 18 in number, are mostly 

 several times shorter than the caulicle, usually not longer than its 



* Seeds from closed cones of P. contorta, two to eiglit years old when I collected them 

 in Colorado, and then kept four years in a hot garret^ germinated freely with Prof. Sargent 

 of the Arnold Arboretum, Mass. 



