2C4 



MORPHOLOGY 



veins that branch dichotomously, except in certain forms with very 

 narrow leaves. In some forms the leaves are short and obovate, sug- 

 gesting those of Gink- 

 goales. The structure of 

 the leaves is like those 

 of the cycads, with the 

 very characteristic meso- 

 phyll (see p. 193). In 

 form, therefore, the leaves 

 in general resemble those 

 of the conifers; but in 

 structure they resemble 

 those of the cycad line. 



Strobili. The strobili 

 are small and monospo- 

 rangiate, both kinds of 

 strobili usually occurring 

 on the same plant (monoe- 

 cious), characters which 

 belong to the conifers. 

 They occur in clusters 

 on lateral branches (fig. 

 461), and both kinds are 

 sheathed by bracts. 



Staminate. The stam- 

 inate strobilus is made up 

 of spirally arranged sterile 

 bracts, among which the 

 stamens occur, either soli- 

 tary or grouped near the 

 apex (fig. 462). Each 



FIG. 461. Restoration of Dorycordaites, one of i j . 11 



., ? . , , . 111- 1.1.. i stamen is a slender stalk 



the Lordaitales, snowing the branching habit, the 



simple, elongated, parallel-veined leaves, and the bearing a terminal cluster 



clusters of strobili borne on lateral branches. After o f three to six erect SpO- 



rangia with longitudinal 



dehiscence. It is only among the Cycadofilicales that such terminal 

 and erect microsporangia are found (cupule type, see p. 184). 



Ovulate. The ovulate strobilus is made up of conspicuous over- 

 lapping bracts, in whose axils short branches appear, each of which 



