. Heredity and evolution in plants . e seed-bearingcones present, the latter unquestionably representing the culminant fruit-producing period in the life of this cycad; 5 (over lower arrow), the ovulatestrobilus, shown at the right, in its natural position, this photograph havingbeen made before the cone was cut out by a cylindrical drill. X At right, longitudinal section of the small ovulate strobilus cut fromits natural position on the trunk as denoted by the arrow s, in photographi. c (upper arrow), seed with dicotyledonous embryo preserved, cotyle-dons being similarly present in the l
. Heredity and evolution in plants . e seed-bearingcones present, the latter unquestionably representing the culminant fruit-producing period in the life of this cycad; 5 (over lower arrow), the ovulatestrobilus, shown at the right, in its natural position, this photograph havingbeen made before the cone was cut out by a cylindrical drill. X At right, longitudinal section of the small ovulate strobilus cut fromits natural position on the trunk as denoted by the arrow s, in photographi. c (upper arrow), seed with dicotyledonous embryo preserved, cotyle-dons being similarly present in the lowermost seed on the left-hand sideof the strobilus; s, traces of hypogynous staminate disk; b, bracts; I, leafbases. X 5. (After Wieland.) 214 HEREDITY AND EVOLUTION IN PLANTS the genus-name, Other forms, usually foundas casts, are called Williamsonia, still others are knownmainly as genera founded on leaf imprints. 144. Cycadeoidea.—In most of its purely vegetativecharacters, such as the anatomy of the stem and the. FIG. 98.—Cycadeoidea Wiclandi. Longitudinal section through theaxis of a female inflorescence, or cone. /, old leaf-base; d, insertion ofdisc; s, erect seed, borne at summit of seed-pedicle inserted on convexreceptacle; b, hair-covered bract. (After Wieland.) structure of the leaves, Cycadeoidea resembled moderncycads, but its reproductive branches were character-istically lateral, which is one of the most fundamentalcharacteristics of the higher seed-bearing plants of to-day. Only two modern^cycads (Macrozamia and Bow- 1 Cycadeoidea Buckland = Bcnncltilcs Carruthers. THE EVOLUTION OF PLANTS 215 enia) have lateral seed-bearing cones (Fig. 95) j1 in theother genera the carpellate cones are terminal (Fig. 96).Various structural characters of Cycadeoidea are shownin Figs. 92-100. In Cycadeoidea dacotensis the flower, which in somespecimens was 5 inches long, was a strobilus, consisting ofa thick axis^on the lower part of which were numerous
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