﻿DESCRIPTION OF PLATES. 275 



the planes a to d, respectively. Owing to the elongation of the receptacle the vertically- 

 inserted seed pedicels are cut through their entire length in transverse section la. (la, S. 

 400; lb, S. 401; ic, S. 402; id, S. 403.) 



Photograph 2. — Cycadeoidca Marshiana (T. 229). X about 0.17. From Minnekahta, 

 in the Southern Black Hills. The arrow indicates the strobilus shown in section by photo- 

 graphs 1, la-id, as borne on the trunk in its natural position previous to removal and sec- 

 tioning. [T. 229 was doubtfully assigned by Ward to C. Minnekahtensis.] 



Photograph 3. — Longitudinal section of seeds from a section parallel to S. 400. It is 

 doubtful if these seeds were fertilized. A small clear space in the more or less collapsed 

 nucellus of the seed to the right is not believed to be an archegonium. 



Note. — Cf. small ovulate cone, photograph 4, plate xliv, also borne by T. 229. 

 Such compared with forms like the present always suggest the possibility of dehiscent 

 staminate disks and a monoecious habit, with the pollen-bearing axes morphologically 

 but not functionally bisporangiate. That most cones have earlier borne a dehiscent 

 disk and are simply young is, however, the view taken in the study of the very similar 

 trunk 214. 



Plate XXXIV. Bisporangiate Strobilus of Cycadeoidca dacotensis in 

 (1) a longitudinal and (2) corresponding transverse section. 



Photograph I. — Cycadeoidca dacotensis Macbride. Four times natural size. Long- 

 itudinal section through the summit of an unexpanded bisporangiate strobilus cut by the 

 writer from a splendid example of a branching trunk and cotype in the collection of the 

 State University of Iowa, Iowa City, Iowa. The original specimen was collected by Prof. 

 Thomas Macbride at Minnekahta, in the Southern Black Hills, in 1895. at the same time as 

 the type of the species. The present and accompanying serial transverse sections cut from 

 this same strobilus belong to the museum of the State University of Iowa. In all these 

 sections preservation is unusually perfect. The synangia are yet closed and the indehiscent 

 sporangial loculi frequently filled with preserved pollen grains nearly or wholly mature. As 

 will be noted in the photograph, the pinnules of the once-pinnate decurved fronds are 

 thickly set with synangia, and so regularly inturned as to be cut throughout quite their 

 entire length, one after another, with a diagrammatic regularity. The section itself is 

 exquisitely iron-stained and an object of rare beauty. 



Photograph 2. — Cycadeoidca dacotensis (T. 214). S. 481. X 5- Transverse section 

 of bisporangiate strobilus and enveloping bracts cut relatively at or a centimeter beneath 

 the level of the base of upper photograph and but a short distance below the level of disk 

 division into separate fronds. It may be noted especially that the megasporophyll zone of 

 the central ovulate cone is not so far advanced in growth as in the State University of 

 Iowa specimen. 



Plate XXXV. Cycadeoidca dacotensis. Transverse Sections through Bispor- 

 angiate Strobili. (Illustrations from same strobili as those of plate xxxiv.) 



Photograph 1. — Transverse section from the same strobilus as the upper photograph 

 of plate xxxiv. Cut near level of summit of central cone and above the division of disk 

 into discrete fronds, of which nine arise on the semi-circumference. X 2.66. 



Photograph \a. — Transverse section parallel to and about 2 centimeters beneath the 

 preceding section, cutting the enveloping bracts, the undivided disk, the decurved frond 

 tips with a few synangia, and the central cone. X 2.66. (A section of the disk, with two 

 appressed frond tips, the lower of which bears a single synangium, has floated to the left, 

 slightly out of the natural position.') 



Photographs 2-2C. — T. 214. Serial sections 481-484, respectively. All X I-33- Cut 

 transversely from fruit I, as drilled from the parent trunk in the form of a cylindrical core. 



2. Section cutting a leaf base, the bracts series, the disk and decurved frond tips, and 

 the central strobilus. S. 481. For enlarged view of disk and cone see lower photograph, 

 plate xxxiv. 



