DIV. II 



GYMNOSPERMAE 



605 



well known as that of the existing Gymnosperms. The Cordaitaceae were loft}-, 

 branched trees with linear or broad and lobed leaves with parallel venation. 

 Their flowers differ considerably from those of recent Gymnosperms. The 

 male and female flowers are borne on spike -like axillary inflorescences. The 

 female flower consists of a single atropous ovule with some bracteoles at its 

 base ; these resemble the vegetative foliage leaves (Fig. 598, 3, 4). At the 

 summit of the nucellus is a deeply sunken pollen chamber in which pollen grains 

 are often met with. The male flowers terminate small shoots that are surrounded 

 by a number of sterile bracts and at the summit produce a number of stamens 

 each of which has 2-4 anthers (Fig. 598, 1). An important fact as bearing 

 on the phylogenv of the group is the presence of a male prothallus as a small 



FIG. 599. Reconstruction of the longitudinal section of the flower of C><"/"'''"t (Bennettites) 

 ingens. (From SCOTT after WIELAXD.) 



multicellular body (Fig. 598, 2). The ovules and seeds show great structural 

 agreement with those of Cycas and Ginkgo. With the exception of some less 

 common fossils (Cycadites, Dicranophyllum), which may be placed with the Gink- 

 goineae, Cordaitcs is the most richly represented type of Gymnosperm found in the 

 Carboniferous rocks. Undoubted Cycadophyta make their appearance in the 

 lower Rothliegende. 



The Cordaiteae disappear in the lower Mesozoic strata. The Gymnosperms 

 flora can be followed through the Trias, in which it consisted of extinct types 

 of Cycadophyta, Giukgoineae, and Coniferae, to the Jurassic period. In the 

 latter it attained a great development in that both the Ginkgoineae and the 

 Cycadophyta attained their maximum development. 



Bennettitaccac. SCOTT has recently given an account of the appearance and 

 the high degree of organisation attained by the Mesozoic Cycadophyta, from the 

 knowledge obtained by WIELAND'S study of the abundant material found in North 

 America. The name Cycadeoidea proposed by the American author is synony- 



