﻿DESCRIPTION OF PLATES. 279 



(.r) through the cortex (c) into the peduncle and axillary leaf base is traversed by this 

 section. Especially to be noted is the downwardly directed elbow of the most nearly axillary 

 leaf to the right, apparently produced by the growth and emergence of the peduncle. The 

 accompanying serial transverse sections are from the same half of the cylindrical core as 

 the longitudinal section, and their planes were originally indicated on the section by the 

 graphite lines and Roman numerals 1 to vn, an inconvenient notation for use in plate 

 legends ; whence the transverse sections photographed are in addition indicated in their 

 respective positions by the section number at the right of the photograph. 



Photographs 2-7. — Twice natural size. Transverse sections 371, 373. 377, 379, 380, and 

 381, from the same half of the same fruit as the accompanying S. 369, photograph 1. The 

 arrows indicate direction vertical to the trunk. Section 381 traverses the conical mass of 

 bracts and bract hairs several centimeters above the outer armor, or trunk surface. The 

 most interesting section is No. 380 (photograph 3), passing through the apex of the peduncle 

 and disclosing no distinct fronds or central cone. Several sections were cut through the 

 summit, but No. 380 is the best. There is a slight but not definite suggestion of division 

 into segments. Section 371 (photograph 7) is of interest as passing tangentially through 

 the woody cylinder of the trunk or trellis of collateral bundles, in the meshes of which 

 large crescentic bundles are seen to arise, with the xylem above and phloem beneath. The 

 leaf bases surrounding the present fruit are still young and the immense size of the areas 

 of radially arranged centrifugal xylem — the only bundle element preserved — is noteworthy. 

 A vegetative rather than a fruiting branch might at first have much the appearance of the 

 present axis, although bracts or scale leaves appear throughout the Cycadeoidese to be 

 mostly characteristic of axes of fructification. 



Plate XLII. Cycadcoidca dacotensis. Serial Thin Sections through a Young 

 Ovulate Strobilus. Tenth axis studied from T. 114. [Cf. figure 89, x.] 



Photograph 1. — S. 540. X 2. Longitudinal section through a small cylindrical core, 

 cutting an ovulate strobilus and a portion of its peduncle in the median vertical plane. The 

 present longitudinal section was made after the three transverse sections a, b, and c were 

 cut, by cementing the four resulting segments of the fruit together again in their natural 

 position, recorded by a plaster mold as described in Chapter III. The present is believed 

 to be the first instance of the cutting of complete complementary longitudinal sections from 

 silicified plants. As in other such strobili from T. 214, remnants of an hypogynous and 

 dehiscent disk are unmistakably present. 



Photograph lb. — S. 538. X 2. Transverse to preceding in vertical plane b. Interest- 

 ingly enough, several isolated synangia appear between the cone and the appressed ramentum. 

 One such may be seen plainly in the present view just below the arrow as it crosses the 

 space between the cone and ramentum to the right. 



Photograph ic. — Central portion of S. 537 (transverse to 540 in plane c). X 5- 



Plate XLJII. Ovulate and Bisporangiate Strobili of Cycadcoidca in various 

 Stages of Growth and Development. 



Photograph 1. — C. Colei (?). S. 284. X 3-2. A very young ovulate cone cut in 

 slightly oblique direction, showing a seed pedicel zone bounded by ramentum on one side 

 and a shoulder (D) on the other side. Whether an aborted disk is indicated or a non- 

 fertile disk, or a dehiscent matured staminate disk, is not determined. Needless to say. in 

 such an instance as the present, such facts can as little be determined from a single section 

 as from serial sections from a single fruit. All the facts can be learned only from longi- 

 tudinal and transverse sections cut from a considerable number of axes borne by the same 

 trunk; even then the results from trunks in different stages of growth must be further 

 compared. 



Photographs 2 and 3. — Sections 114 and 136. X 3-2. (C. Paynci?) Transverse sec- 

 tions through basal portion of a disk-bearing axis (2) and its peduncle (3I. It is especially 



