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APPENDIX A 



rather small; but others grew to giant size, with massive trunks supported at the 

 base by four to seven spreading branches (stigmaria), which penetrated the soil 

 and bifurcated again and again, and to which were attached the short true roots. 

 There were two chief types of these trees — *Sigillaria and *Lepidodendron. 



*Sigillaria (Figs. 26.11 and A. 16) had an unbranched or few-branched trunk 

 which in some species attained a height of 70 to 100 feet. The top 10 feet of the 

 trunk surface was clothed with erect or drooping grasslike leaves, only a few 

 inches long in some species but several feet long in others. Where the leaf bases 

 dropped from the trunk they left a scar, the form and arrangement of the scars 

 differing with the species. In Sigillaria the scars are typically in vertical rows, and 

 look like repeated impressions of the same seal or stamp, whence the name seal 

 tree (Latin, sigilla, "a seal or mark"). 



mgs 



Fig. A.15. The "little club moss" Selaginella. A, the sporophyte plant. B, a sporangia- 

 bearing shoot. C, the swimming sperm. D, section through the microsporangium. E, section 

 through the megasporangium. rncs, microspore; mcsp, microsporophyll; mcspm, micro- 

 sporangium; mgs, megaspore; mgsp, megasporophyll; mgspm, megasporangium. {Modified 

 from Turtox chart, courtesy General Biological Supply House, Inc.) 



*Lepidodendron (Figs. 26.11 and A. 17) means scale tree (Greek, lepis, "scale," 

 and dendron, "tree"), referring to the fact that the leaf scars were arranged in 

 spirals to give a fish-scalelike pattern. Over 100 species of this genus are known; 

 some of them had trunks which rose well over 100 feet to the base of the 20 foot 

 crown of forking branches. The leaves were usually only a few inches long and 

 covered the upper parts of the trunk and branches. Both Sigillaria and Lepidoden- 

 dron produced microspores and megaspores, borne on sporophylls grouped into 

 conelike structures. The microspores were shed in such vast numbers that they 

 make up a considerable part of the carbonized plant material that is coal. 



Subphylum IV. Pteropsida (ter op' si da). The Ferns and Seed Plants. 



The reasons for including the ferns and seed plants in one subphylum 

 are too technical to elaborate upon; they include such considerations as 

 the position of the sporangia on the lower instead of the upper surface 

 of the leaves or sporophylls, the presence of leaf gaps in the vascular 

 cylinder, etc. Broadly speaking the Pteropsida are the large-leaved 



