﻿DESCRIPTION OF PLATES. 



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and on its right side another row of synangia, nether to the plane of this section. The 

 pinnules p' and p 3 are borne by the frond rachis (f) of the disk, and pinnule /> a bears the 

 two vertical rows of synangia in the middle of the photograph so characteristically disposed 

 in interlocking vs; whilst the pinnule p 3 bears on its left side the row of ten synangia 

 seen to the right of the photograph in part. 



Photograph 4. — S. 104. X 8. Radial longitudinal section of strobilus, passing through 

 pinnules lengthwise (in a plane at right angles to section no). The section passes through 

 the distal half of three successive pinnules all the way to the tips, the area shown being 

 near the summit of the central ovulate cone. 



Photograph 5. — S. 107. X 9- Radial longitudinal or slightly tangential section of 

 strobilus from nearly same position as section 83, photograph I. Note large synangium 

 cut longitudinally. 



Photograph 6.— Enlarged view of a section passing through a portion of a synangium 

 in the lateral longitudinal plane, and through a portion of another synangium in the trans- 

 verse direction. In both these synangia the sporangial loculi are filled full with pollen grains, 

 and much pollen is present in the loculi of all the sections illustrated on the present plate. 



Plate XXXVIII. Young Fructifications and Other Structures of 

 Cycadeoidere. 1, 2, 4, Cycadeoidea; 3, Cycadella. 



Photograph 1. — Cycadeoidea dacotcnsis (T. 214). S. 561. Natural size. Fruiting axis 

 xiv. For position on trunk see text-figure 14. Transverse section of an axis of fructifica- 

 tion cut from trunk, together with surrounding leaf bases, in the form of a cylindrical core. 

 The section passes 4.5 cm. beneath surface of armor. (Cf. photograph 2.) See page 181. 



Photograph 2. — S. 560. Natural size. Transverse section through same axis as the 

 preceding. Cut 2.5 cm. above S. 561 (2 cm. beneath the surface of the armor'), and disclos- 

 ing the presence of a small apical ovulate cone. The large size of the peduncle and the 

 numerous bracts, with the small size of the seed zone and broken-down condition of most of 

 the cone tissues, suggest the failure of the cone to develop following maturity and dehis- 

 cence of a staminate disk. But while this particular axis may not have been functionally 

 bisporangiate others amongst the sixteen axes studied from T. 214 appear to have been 

 truly bisexual. 



Photomicrograph 3. — Cycadella ramentosa. Transverse section through ramentum of 

 leaf bases. Heavy type of ramental scale two or three cells thick. X no. 



Photomicrograph 4. — Cycadeoidea dacotcnsis. Transverse section through ramentum 

 of bracts (the Cyathea type one cell thick) and the bract itself. X 20. 



Plate XXXIX. Cycadeoidea dacotensis. Sections of young axes of fructifica- 

 tion cut from T. 214 in form of cylindrical cores. All natural size. 



Photograph 1. — S. 512 (axis vi). (For position of this and other axes cut from T. 214 

 see text-figure 14, and the two other figures, 89 and 94.) Radial longitudinal section of 

 trunk cutting through the medulla (m), xylem (x), cortex (c), and armor, so as to pass 

 through the entire length of a young fructification and its cortical bundle trace in the 

 median vertical plane. Only the barrel-shaped peduncle densely set with hairy bracts has as 

 yet developed. This young axis is one of six quite regularly disposed circularly about the 

 crown of non-emergent young leaves at the summit of the trunk. All six projected as 

 conical masses of ramentum rising three or four centimeters above the armor, and are 

 evidently in much the same incipient stage of growth or arrested development, as the case 

 may be. The arrow to the right indicates the relation of the section to the axis of the 

 trunk. (The terminal ramentum is present in the section to a distance of about three centi- 

 meters further than shown in the photograph.) (See figure 95.) 



Photograph 2. — S. 520 (axis vm). Transverse section of a cylindrical core passing 

 from the cortex into the armor in an obliquely tangential plane to the trunk. The present 



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