18 



MAZOCABPON OEDIPTEBNUM 



the pedicel attachment, and this is where 

 the sporangium breaks loose first (com- 

 pare pi. 1, figs. 2 and 4). Two or three 

 other thin areas, as shown in plate 2, 

 figure 4 (T), also seem to mark natural 

 lines of weakness where breaks in the 

 sporangial wall can easily occur. 



The female gametophytes agree in 

 general with those of Selaginella and 

 Isoetes except that only a single very 

 large archegonium is produced in each 

 megaspore. Proximally toward the 

 apices and around the individual arche- 

 gonia the cells are smaller and more 

 delicate, as shown on plate 4, figure 5, 

 and also in figures 2 and 4. In figure 

 2 the gametophyte is somewhat frag- 

 mented within the megaspore coat, but 

 the tissue that remains has been trans- 

 formed into material having all the 

 characteristics of fusain and is fairly 

 well preserved. A single archegonium 

 is also present, although the section il- 

 lustrated cuts it tangentially and its 

 full diameter is not shown. Plate 4, fig- 

 ure 4 illustrates another megaspore 

 which is similar in most respects but 

 shows the gradation in gametophytic 

 cell size, distal (largest) to proximal 

 (more delicate cells), the best of those 

 shown here. This gametophyte appar- 

 ently shrank away from the distal spore 

 coat before becoming partly fusainized 

 and mineralized. Figures 8 and 9, plate 

 3, represent a section across the apical 

 prominence of a megaspore and an 

 archegonium which is cut above the 

 middle so that its full diameter is not 

 shown. A spherical red humic body, 

 somewhat suggestive of an egg nucleus, 

 lies in the center of the archegonial 

 cavity. Figures 5, 6, and 7, plate 3, 

 show part of a series of longitudinal 

 sections through an archegonium. Fig- 

 ure 5 illustrates a median section which 

 shows that the archegonium is pyrif orm, 

 with a very short neck that protrudes 

 slightly into an external cavity, or ves- 

 tibule, just below the spore coat apex. 

 A deposit of dark humic material part- 

 ly fills the venter of the archegonium 

 and obscures some of the cellular de- 

 tails. The venters average about 250 /x 

 in transverse diameter, being much 

 larger than those known in other fossil 

 or modern cryptogams, few of which 



attain a diameter of 100 /x. Gymnos 

 permic archegonia are generally more 

 than twice as large, but it appears that 

 the largest cryptogamic archegonia 

 known are these from Mazocarpon. 



In two instances a small globular 

 group of 8 to 12 cells was observed 

 which may represent young embryos 

 within apical cavities that may accord- 

 ingly correspond to venters of arche- 

 gonia after fertilization. These are 

 shown on plate 3, figures 1 and 2. 

 Figure 3 show^s the structure in figure 



2 at lower magnification. The spore 

 from which. figure 1 was obtained is the 

 same as that illustrated at lower magni- 

 fication on plate 2, figure 3. Since 

 gametophytic tissue is not preserved 

 except near the apex of these spores, 

 and since the globules of 8 to 12 cells 

 mentioned show no differentiation of 

 tissues, one cannot be certain of their 

 embryonic nature. If the two respective 

 cellular globules do represent embryos, 

 the original archegonial cavities must 

 have shrunk by inward proliferation of 

 cells, since both the apical cavities are 

 smaller than in normal prefertilization 

 archegonia. The available series of sec- 

 tions demonstrates that the ''embry- 

 onal" group of cells shown in figure 2 

 is free of any attachment to the wall 

 of the cavity which surrounds it. The 

 fact that two similar ''embryonic" 

 globules have been found shows at least 

 that these structures should not be 

 dismissed as meaningless. 



Microsporangiate cones which are 

 identified as forma microphortcm are 

 shown on plate 5, figures 1 and 3. The 

 first represents a longitudinal and trans- 

 verse section at the tip of a cone. The 

 cellulose peel from which this photo- 

 graph was taken extended over both 

 transverse and longitudinal surfaces so 

 that the register of structure in the 

 two opposite planes is perfect. Figure 



3 is a similar peel taken at the base of 

 another cone. Although most of the 

 sporangial walls are broken at one or 

 two places, the majority of the micro- 

 spores have remained in place. This is 

 fairly common in this material, in con- 

 trast with the usual condition of preser- 

 vation of Lepidostrohios in which the 

 spores usually have been shed. Some 



