SPECIFIC COMPARISONS 



23 



merges there with the upturned lamina. 

 Lamina rises to the third rank above, hence 

 was probably about 10 mm. long. Lamina is 

 about 6 mm. broad and spoon-shaped at its 

 base; laminal outgrowths on either side of 

 the pedicel are not as broad as in M. oedip- 

 ternum. Dorsal heel nearly lacking; sporo- 

 phyll is thickened at the juncture of lamina 

 and pedicel but extends downward only 

 about 8/10 mm. below the plane of the 

 pedicel. (Cf. p. 580, op. cit. It is evidently 

 a mistake where it is stated, op. cit. p. 576, 

 that this "convex cushion might be 8 mm. 

 below the plane of the keel.") Megasporan- 

 gium is about 5 mm. in length, 2.6 mm. in 

 height, and attached to a ventral ridge of 

 the pedicel. Traces of a ligule are reported 

 situated in the sinus distal to the sporan- 

 gium. The sporophyll trace extends the 

 length of the ventral ridge instead of in 

 the pedicel itself and recurves downward 

 at the distal end to enter and supply the 

 lamina. The sporangium is somewhat nar- 

 rower adjacent to the axis and broader dis- 

 tally. Externally it is marked by a keel 

 ("sporangial lamella") extending on the 

 sides and around the distal tip of the sporan- 

 gium. Position of the keel on the sides of 

 the sporangium is somewhat uncertain. 

 Miss Benson's much copied text figure 1 (op. 

 cit. p. 571) shows the keel recurved upwards 

 and only carried toward the axis about mid- 

 way, high on the side of the sporangium. 

 Her photographs of tangential sporangium 

 sections (figs. 1 and 16, pis. XVII and XVIII, 

 op. cit.) show the keel low on the sides. 

 It would seem probable that the photographs 

 show its position more accurately. The spor- 

 angium and its keel are covered externally 

 with a characteristic prismatic cell layer. 

 As many as eight large (about 2 mm. di- 

 ameter), radially symmetrical, piano- or 

 concavo-convex, strongly apiculate mega- 

 spores are contained in each megasporan- 

 gium. The spores are in a definite arrange- 

 ment around the periphery, with their apices 

 oriented toward the center of the sporan- 

 gium. Intrasporangial tissue fills the central 

 part of the sporangium, more or less en- 

 closes each of the megaspores, and margin- 

 ally lends rigidity to the sporangial wall. 

 External to the megaspores this tissue is 

 only a few cells thick except in spore in- 

 terstices and in the sporangial keel. Some 

 megaspores, either isolated or in partially 

 disintegrated sporangia, possess gametophy- 

 tes. At least two archegonia may be pro- 

 duced subjacent to the spore apex. Prom 

 Miss Benson's plate XVII, figure 3 (op. cit.) 

 the venters appear to be at least 200 /i in 

 diameter. 



The details of the male cones (or portions 

 of cones?) and of the microsporangia are 

 much less satisfactorily known. It seems 



Fig. 5. — Diagrammatic representation of 

 Mcizocarpon oedipternum; a, megasporophyll 

 in transverse section near the middle; 1), por- 

 tion of megasporangiate cone in longitudinal 

 section; c, diagrammatic representation of 

 Mazocarpon shorense; based on information 

 summarized from Miss Benson (1918). Dia- 

 grams a-c drawn to the same scale. 



