ENGELMANN REVISION OF THE GENUS PINUS, ETC. 169 



aster) or lacerate {P. Lainbertiana) crest, or it terminates in a 

 knob or a few teeth (in most Strobi and a few Pinasters such as 

 P. Balfouriana and sylvestris). 



The POLLEN has the well known bilobed form, consisting of 

 an elliptic central portion, which emits the pollen tubes, and two 

 lateral sacs which are said to contain air. The longer diameter 

 measures 0.025 to 0.045 litres, mostly between 0.030 and 0.040 

 lines, while the pollen grains of Abies and Picea are much 

 larger and in many instances twice as large, viz. 0.045 to 0.070 

 lines long. Thus by the pollen alone Pinus can generally be 

 distinguished from those allied genera. The different species of 

 pines are pretty constant in the size of their pollen. 



Without going into minute detail, I will only state that I find 

 pollen grains of 



0.025-0.030 lines in P. edulis and P. Batiksiana ; 



0.030-0.035 " in P. Balfouriana, sylvestris, jnofiiana, resinosa, 



Chikuahuana, Laricio, tnofs, contorta; 

 0.035-0.040 " '\n P. Strobiis, excelsa, Pinea, rigida, Tceda, mitts; 

 0.040-0.045 " in P. Lainbertiana, Jlexilis, Montezumce, Pinaster, 

 ponderosa, Sabiniana, Elliottii. 



The property of the pine-pollen to float for a long time in the 

 air, and to be carried by storms to very distant localities, is well 

 known. I have found in streets of St. Louis after a rainstorm 

 from the south, in March when no pines north of Louisiana were 

 in bloom, pine-pollen which must have come from the forests of 

 F. aiistralis on Red river, a distance of about 65 degrees of lati- 

 tude or 400 miles in a direct line. 



The FEMALE FLOWER consists, as in all Abietinece, of a car- 

 pellary scale in the axil of a smaller, concealed, bract, bearing two 

 pendulous ovules on the lower part of the upper side. A number 

 of such scales in the axils of their supporting bracts, and spirally 

 arranged, form the female ament. The question of the nature 

 of the scales, and of the ovules they bear, is not to be discussed 

 here, but it may be stated that the best lights force the view on 

 us that the carpellary scale consists morphologically of two leaf- 

 organs, lateral to an undeveloped axis and united at their poste- 

 rior edges (those turned towards the axis of the ament), and thus 

 bearing their naked ovules on their morphologically outer but 

 now reversed and apparently upper side. 



