HALLE, ON THE SPORANGIA OF SOME MESOZOIC FERNS. 7 



several authors. There is no evidence, however, that the wall 

 is ever perforated at the apex. The cells of the sporangial wall 

 can be fairly clearly seen on using a high power preparation 

 lens (compare pi. 1, figs. 5, 6). They appear to be uniform all 

 over the sporangium: there cannot be observed any differentia- 

 tion of the tissue to indicate the existence of an annulus. It 

 is possible that there may be a zone of cells with thickened 

 walls, as in Angiopteris, but no trace thereof can be detected, 

 even on the most careful examination. 



In the specimens in figs. 5 and 6, there is seen along one 

 side of the sporangia a fine but distinct longitudinal furrow, 

 running from the apex to the base. This line evidently marks 

 the stomium or the place of dehiscence. In another specimen, 

 pi. 1, fig. 3, of which a part is shown in higher magnification 

 in pi. 1, fig. 12, the sporangia seem to have reached a later 

 state of development. They are open, and in some places show 

 a longitudinal slit corresponding to the stomium. 



The exact arrangement of the sporangia is somewhat 

 obscured on account of their crowded position. The rows 

 of sporangia appear all uniform, but on a careful examination 

 they are found to be arranged two and two (compare pi. 1, 

 figs. 4 — 7). In each row of sporangia the apical depressions 

 of the sporangia are seen to point in the same direction but in 

 two adjacent rows in opposite directions. Each sorus thus 

 consists of two rows of sporangia, the apical depressions of 

 which were pointed obliquely outwards in the natural state, so 

 that the apices of adjacent sporangia of different sori touch 

 each other in the flattened condition of the sorus in the spe- 

 cimens. This arrangement is somewhat obscured in the speci- 

 mens now described on account of all the sori being a little 

 turned over to one side through pressure at the f ossilization, so 

 that the sporangia of one row of the sorus are seen more from 

 the apex, those of the other more form the side. The true 

 arrangement is more clearly seen in pi. 1, fig. 12, which shows 

 a part of the specimen in fig. 3 in higher magnification. 

 Usually the sporangia cover the lower surface of the pinna 

 entirely, so that the veins cannot be observed. From the an- 

 alogy with recent Marattiaceae it would seem probable that 

 the sori were placed over the veins. The relation between the 

 sori and the veins, however, is more complicated in this plant. 

 The veins in the sterile frond of our plant anastomose near 



