JoHNSON^ — Is Archceopteris a Pteridosperm ? 



127 



phyllacese, as one of the Marattiaceee, and quite recently, as mentioned 

 already, it has been assigned by several writers to the Ptei'idospermeEe. 

 Assuming that my statements as to its structure are reliable, what bearing 

 liave they on its affinities ? One is at once struck by the comparability of 

 the septate sporangium to tlie Ophioglossaceae " sporangiferous spike." In 

 Ophioglossum vulgatum the usually solitary foliage-leaf bears on its upper side 

 the stalked body, whose free end consists of two rows of sunk sporangia 

 opening by transverse slits. Between tlie sporangia (fig. 2) the vascular 

 system of the " spike " sends, right and left, a bundle between each two 

 superposed sporangia. Bower regards this composite body or " sporangiferous 

 spike" as the equivalent of a single sporangium (e.g., that of Lycopodium) 

 which has become septate by the sterilization of potential sporogenous tissue, 

 in which, however, it must not be overlooked, a vascular bundle runs in eacli 

 septum. 



My own inclination is to regard Archseopteris not as a male Pteridosperm, 

 but as a representative of the type of plant from which the Ophioglossacese 

 (and possibly the Osmundacese) sprang, and at the same time, as illustrative of 

 the type from which the Pteridosperms may have arisen. This view has been 

 strengtliened by the appearance I am about to describe, presented by the fertile 

 pinnae in two different fronds. In one case the piece of the frond preserved 

 shows eight or nine pairs of pinnae, nearly all partly fertile. The sporophyllule 

 or fertile pinnule of these pinnae shows the usual characters as described ; 

 but it shows, in addition, from the under side, a sterile, more or less wedge- 

 sliaped lobe, wliich may be itself lobed (PI. V., fig. 4 ; Text, figs. 4, 5, and 1). 



Fig. 4. 



Fis. 5. 



Thus in the one pinnule we have a sterile lower abaxlal' lobe and a fertile 

 upper adaxial lobe. I have seen both lobes sterile and also both lobes fertile, as 

 exceptions. On a small scale we have roughly represented, repeatedly in the 

 one pinna and frond, the normal solitary condition of things inOphioglossum. 

 It may be urged that this specimen of Archaeopteris is abnormal, and that 



' The terms Abaxial and Adaxial seem preferable to " dorsal " and " ventral," which are used in 

 one sense by Continental writers, and in the opposite sense by some English writers. Seward uses 

 the terms, no doubt inadYertently, in both senses in " Fossil Plants," vol. ii. 



