﻿DESCRIPTION OF PLATES. 27 1 



3. Transverse section of the central concentric bundle of a fertile pedicel, with larger 

 cells of enveloping cortex shown in part. X 225. 



4. C. Wielandi (T. 77). S. 2. X about 35. Insertion of pedicels and scales on recep- 

 tacle in longitudinal section. 



5. Pedicel from another cone cut transversely in the basal legion. Included in this 

 plate for comparison with photograph I, where the seed pedicels are cut but a short distance 

 beneath their summits. Note the great increase in the number of cortical cells and decrease 

 in their size towards the insertion of the pedicels. X 3°. 



Plate XXVIII. Sections from ovulate cones of the Cycadeoidere. Seed struc- 

 tures (with figure 7, further illustrating insertion of seed pedicels and inter- 

 seminal scales). 



Photomicrograph 1. — C. Wielandi (T. 393). S. 108. X SO. Longitudinal section 

 through a seed. After passing through the seed base very nearly in the median vertical 

 plane this section cuts just beneath a much flattened portion of the integument and then 

 finally passes outside the integument. The conserved tissue in the central and basal third 

 of the seed is plainly a depressed portion of the nucellar wall. The slightly convex flattened 

 or even concave lateral surfaces of the various forms of asymmetric: seeds to be noted in 

 the accompanying transverse section, photograph 6, illustrate how, as in the present instance, 

 a large lateral area of the nucellus or of the integument may appear in a longitudinal section. 

 The chief structures present are indicated as follows : s, seed pedicel, about two-thirds of 

 the diameter being made up of the ensheathing cortical husk, which thins out to a single cell 

 in thickness half way up the side of the seed and may disappear entirely; v, the single cen- 

 tral concentric bundle of the radio-symmetric pedicel passing into the chalazal region ; p, 

 short, nearly cubical palisaded cells a single cell in thickness, forming the true outer layer of 

 the seed as set in the basal cup-like extension of the cortical husk ; hf, fibrous hypoderm. 

 may be heavier-celled below; al, abscission line between hypoderm and chalazal region; c, 

 chalaza, mainly composed of scalariform tracheids (the present photograph is much too 

 little magnified to disclose the scalariform markings, which are very distinct throughout all 

 the chalazal region) ; n, nucellus, with lower third of the nucellar wall tissue preserved and 

 in appearance much like the wall-tissue of the sporangial loculi. At the upper left-hand 

 corner of the photograph there is a darker area which examination of the original section 

 shows to be a rather indistinctly preserved portion of the palisade iayer, with the nucellar 

 wall underlying. 



The foregoing structures find their closest known and almost identical parallel 

 in the several times larger Paleozoic seed Lagenostoma Lomaxi. Whether or not 

 there is a series of diminutive or vestigial vascular bundles disposed about the cir- 

 cumference of the megaspore as in Lagenostoma has not been determined ; though far 

 more reduction than in that form is evident. 



From a petrographic point of view the present section, be it further noted, is of 

 much interest because of the fact that its several tissue systems, from thick-walled 

 and woody fibers to the most delicate cellular tissues, are alike traversed by numerous 

 remarkably clear and distinct phenocrysts with but slight disturbance of the cell walls. 

 These phenocrysts hence formed after the strobilus was silicified ; there being here 

 afforded a clear instance of a solid or semi-solid behaving as a solution, under con- 

 ditions producing in some instances pheno- and in others sphaerocrysts. 



Photomicrograph 2. — Cycadeoidea dacotensis (?). X 20. A younger seed than the 

 preceding, with two of the characteristic surrounding infertile scales, between which projects 

 the entire length of the micropylar tube. Partially collapsed nucellus distinct. 



Photomicrograph 3—Bennettites Morierei Saporta et Marion. Longitudinal section 

 through three consecutive seeds cut by Professor Lignier from the original type. X 10. 

 From the Oxfordian Jurassic of Vaches Noire, Villers-sur-Mer, Calvados, France. For 

 comparison with the seed tips to be seen in photographs 2 and 4. The most clearly marked 



