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REPRODUCTIVE STRUCTURES. 



that were the frond unfolded all the pinnules would lie in parallel succession in 

 two ranks rising at the same angle to the respective rachides. 



Let us now turn to the series of transverse sections cut from these same stro- 

 bili, taking up, for convenience, first, the section cutbasally just below the insertion 

 of the ovulate cone and the surrounding staminate organs. (See fig. 73, I, and 75 b.) 

 In this section it is seen that the receptacular region is not of large diameter and 

 is followed exteriorly by the system of hairy bracts, and then by the leaf bases. 



In the second transverse section, figure J3, n, which is cut about 1 cm. above 

 the strobilar insertion, the central cone is prominent, and all its parts well marked. 

 Resting against it are the later- 

 ally oblong transverse sections 

 of the free flattened rachidal 

 tips, these being followed exteri- 

 orly by a broad annulus of deep- 

 ly stained tissue. This latter 

 is the transverse section of the 

 peduncular region of the stami- 

 nate series and shows at once 

 in connection with the longi- 

 tudinal sections just examined 

 that the bases of the individual 

 staminate organs are not free 

 but fused into a heavy and 

 strongly marked bell-shaped 

 disk. Surrounding this are the 

 copiously haired bracts, while 

 exteriorly to these several leaf 

 bases may also be noted. In 

 the succeeding transverse section, figure 

 preceding, the central cone is of markedly less diameter, and is succeeded by 

 the laterally compressed irregularly rhombic transverse sections of the fertile frond 

 ends, which mostly bear a single synangium on each outer (that is, ventral) angle. 

 As thus ranged about the central cone these frond tips are 9 in number in the half 

 circle, and show that the entire disk finally splits up into 18 or 19 discrete fronds. 

 The bases of these fronds are, however, in this, as in the preceding section, still 

 strongly fused, and both the inner and outer borders are much wrinkled, showing 

 that the disk surface was subject to irregular furrowing and crumpling during 

 emergence. Exteriorly follow the bracts and leaf bases as before. 



[In a hypothetical section 8 mm. above in the general relations are the same, 

 but it is especially to be noted that not only are the free tips of the fronds next the 

 seed cone seen to bear synangia, but likewise an inner series of corresponding ridges 

 of the still continuous base of the disk also bear synangia. The central cone is here 

 cut near its summit and the tips of the fronds hence occupy a much smaller circle, 

 and are more nearly rhombic in outline.] In the succeeding section (fig. 73, iv), 

 cut just beyond the tip of the central cone, and 4.5 cm. above the receptacle, the 



Fig. 76. — Williamsonia gigas. From Lignier (85). 



a. Specimen 2406 of the Paris Museum. 2. A bisporangiate strobilus 

 showing apical portion of an ovulate cone surrounded by the regularly dis- 

 posed unexpanded staminate fronds with the curved portion of their rachides 

 broken away so as to expose the son in undisturbed position. (See figures 

 70 and 88.) 



b. Cast of central portion of (a). This specimen is differently interpreted by 

 Lignier. who adjudged the bodies here considered as sori to be seeds. 



73, in, cut a centimeter above the 



