620 



APPENDIX A 



branches bearing many large, simple leaves. In one genus, *Cordaites (Fig. 26.12 

 and 27.20) the leaves sometimes reached a length of 6 feet and a width of 6 

 inches. In other genera the leaves were smaller, sometimes strap-shaped with 

 blunt or sharp tips, and sometimes grasslike, \£ inch in breadth and 20 inches 

 long. The leaves were thick and parallel-veined. 



Separate male and female catkinlike cones were borne on the same tree. The 

 female cones generally matured only a single large seed with a hard seed coat and 

 fleshy rind. The wood of the trunk was much like that of modern pines but had a 

 large central pith. Members of this group showed a combination of the features 

 of seed ferns, cycads, ginkgoes, and conifers, and are thought to have been 

 ancestral to the latter. 



The Maidenhair Trees (Ginkgoales, pronounced ging ko a/ lez in spite of the 

 spelling) are an ancient group of which there is today but a single survivor. The 



maidenhair tree {Ginkgo biloba, Fig. 

 26.15) is almost unknown in the wild 

 state, though extensively in cultivated 

 form. It grows to a height of 90 feet, 

 with freely branched crown. The leaves 

 are flattened and usually bilobed, 

 resembling those of the maidenhair 

 fern. The small, inconspicuous male 

 and female cones are borne on separate 

 trees. Members of this order are known 

 as early as the Carboniferous, and the 

 genus Ginkgo had its origin as early as 

 Triassic time. 



The Conifers (Coniferales). The 

 needle-leaved evergreen trees con- 

 stitute by far the most conspicuous 

 group of living gymnosperms. This 

 is true whether one considers num- 

 ber of individuals, number of genera 



Fig. A. 21. Male cones of the red pine, Pinus 

 resinosa, surrounding a terminal cluster of 

 young leaves ("needles"). {Photo by Prof. 

 E. B. Mains.) 



(46), number of species (nearly 500), size of individuals (many large, the 

 sequoias among the most gigantic living things, with trunks almost 400 

 feet tall), or economic importance. Conifers provide the softwoods of the 

 lumbering industry, pulpwood for paper mills, resin, and turpentine. The 

 group includes the Auracarian pines, now confined to the southern 

 hemisphere but formerly widespread; the sequoias or California "big 

 trees," the ancestry of which can be traced back to the Permian; and 

 the pines, spruces, firs, junipers ("red cedars"), larches ("tamaracks"), 

 cypresses, and yews. In all the conifers, pollen is produced in small male 

 cones and is broadcast on the wind in great amounts; it reaches the female 

 cones wholly by accident. The leaves are needle- or scalelike, and the 

 wood lacks vessels and generally possesses resin ducts. 



