﻿DESCRIPTION OF PLATES. 



26] 



In the second supplementary figure to plate HI, a section parallel to that photographed 

 in the plate as an opaque object is reproduced from a photograph by transmitted light. 

 The pinnules, s, s, s, bear the closely packed synangia, indicated by the masses of pollen 

 rilling the sporangia, the synangial walls not being delimited by color differentiation, 

 although present. The broad vertically and longitudinally cut decurved tip of the rachis, 

 the ascending limb of which bears the pinnules, s, s, is denoted by /. 



Plate IV. Cycadcoidca ingens (type). 



Photographs of polished transverse sections of the bisporangiate flower bud shown 

 in the preceding plate in. Enlarged to a little more than twice natural size. 



Photograph I.— Section from the uppermost of the two saw cuts to he noted in the 

 photograph of the accompanying longitudinal section, plate in. In the present section all 

 1 be main features except the central cone are very distinct. The synangia are especially 



prominent because of the preservation of the pollen. ^ N ^ 



filling completely all the sporangial loculi in milk- ^^ ^^ ^-V \ 



white masses, which stand out clearly and distinctly f ^^^-f^r*$^!s ^\ 



in the gray and translucent to transparent matrix — /J J^j'iT ^I^'^y^As \ A 



the synangial walls not being sharply marked, d /\'^-^ ' ' '^4o \ ^ 



though present. The synangial pollen contents thus If /^<-f'%T^'l..^ify^]i. \ r- 

 show the 13-rayed asteriate arrangement of the J / K^;-,Sm: ^X ; : _.*\\k \ 

 synangia, corresponding to thirteen fronds compos- / • l/jJ*-4" 4j.| Jv! -0 Afi^S \ \ n 

 ing the flower. Of the central cone only some small / / W»/ HMi? ^'^ / // 

 areas of the peripheral portion showing the young [ \ \fi ^ B ■ "' f^ < ''~"Jdl " \~"E 

 seed zone are present, the outline of the com- being \ A \v^.,/, - "yl \ ) - / 



approximately indicated by a cavity lined by a druse V ^ "~^<^_ »vV/ s fj 

 of quartz crystals. All the rachides of the thirteen \ S^^A* — ^ 



staminate fronds are clearly indicated, as well as ' 



the lines showing their sides, which are SO closely Explanatory Figure.- A. group of synangia belonging 



appressed as tO form a capsular bud. The de- to pinnules borne by ihe first and thirteenth rachides: 



curved ends of the fronds are mostly present, but B, rachis numbered 1 ; C. outline of the but partially 



, , jr 1 .1 1 1 f.i- i* preserved central ovulate cone, the former position of 



not so clearly defined at the level of this section. ,.,..,,., ■ , , . •_ ■■ 1 



which is in the fossil mainly taken up by a cavity lined 

 The accompanying Outline (sllOWll in natural Size) by a druse of quartz crystals ; D. synangia of staminate 



affords a key to the Structures present, the letter- frond (111) ; E, ventral I lower) surface of rachis lying 



ing being the Same as 111 the key figure tO the against mass of bract hairs; I. one of the hair-covered 



■ j r 1 -. .. , , , . bracts; 1-XI1I. the staminate fronds. Natural size. 



legend tor longitudinal section shown in plate in. 



Photograph 2.— Section from the lowermost of the two saw cuts to be seen in the 

 photograph of the longitudinal section, plate in. This section is cut approximately through 

 the receptacle of the central ovulate cone and the bases of the staminate fronds, which are 

 seen to be fused into a single clearly outlined continuous disk. As in the other sections all 

 the space between the bracts is densely packed with rather long and silky bract hairs. The 

 bracts are at this height not nearly so flat in transverse section as at the higher level, 

 photograph 1. Their spiral succession is clearly discernible. The features of the bract hairs 

 are illustrated in connection with the description of the young crown of leaves accompany- 

 ing the present flower bud. 



Plate IVa. Cycadcoidea ingens. 



Plan of the bisporangiate strobilus or flower, consisting of a central ovulate cone, an 

 hypogynous staminate disk, and a series of spirally-inserted enveloping bracts, all shown 

 diagrammatically a little under the natural size, and as if pressed out fiat. (Compare with 

 illustrations of Chapter VII and the restoration of an expanded flower facing Chapter VI, 

 noting that in the latter a form with fourteen fronds has been indicated. Although the 

 actual number thirteen would be preferable as the observed number, variations of from one 

 to three fronds in the total number composing the disk are to be expected.) 



