272 Prof. F. 0. Bower. Studies in the [Dec. 17 



systematically nearer to the LycopodinaB ; this relationship has been 

 recognised by various writers on other grounds, and the characters of 

 the sexual generation will even help to support this nearer affinity. 



A special interest will now centre round a small and very rare 

 plant, viz., OpUoglossum Bergianum, one dried specimen of which 

 I received from Professor MacOwan. It appears to show points of 

 affinity both to Phylloglossum and OpUoglossum. While it is obviously 

 an OpUoglossum, it shows (1) in the form of the leaf and the general 

 habit, (2) in the fact that more than a single leaf is exposed at once, 

 (3) in the low point of insertion of the "fertile frond," and (4) in 

 the small number of partitions in it (sporangia, 8 12), characters 

 which suggest that its further investigation would probably disclose 

 facts of the greatest importance. 



The relation of Isoetes to our series will naturally be a close one ; 

 just as the plant of OpUoglossum may be looked upon as a vertical 

 strobilus, of which the large sporophylls are developed in slow suc- 

 cession, so also may Isoetes be regarded as a simple vertical strobilus, 

 but the leaves are more numerous ; the leaf (sporophyll) is relatively 

 large, though simple. The sporangium is, in form, like a flattened 

 cake, inserted on the upper surface of the leaf, near its base ; it also 

 is partitioned, more or less completely, and Goebel has shown clearly 

 in his drawings how the hypodermal tissue, which may here also be 

 styled the potential archesporium, becomes differentiated into sterile 

 trabeculae and sporogenous cells. To this differentiation I should 

 assign a similar interpretation to that in the Ophioglossaceae ; the 

 sporangium is, however, less elaborated, and its size and prominence are 

 not such as to have led to its sporangial character being lost sight of. 



Quite recently, on examining the fine series of sections of Lepido- 

 strobus in the British Museum, I have found processes of sterile tissue 

 which spring from the base of the sporangium, and project far into 

 the mass of spores ; these appear to be comparable to the trabeculae 

 of Isoetes, though differing in points of detail. 



I do not think it desirable as yet to express opinions as to the 

 bearing of this work upon the other Ferns. At present I am disposed 

 to think that the Ophioglossaceae and Isoetes are in an intermediate 

 position between the Lycopods and other Ferns, and that their affinity 

 to the former is certainly quite as close as to the latter. 



The Psilotaceae are probably a separate series, remote from both ; 

 they will be dealt with on a later occasion. 



We have seen how the Ophioglossaceae illustrate, according to our 

 theory, the elaboration and partitioning of a sporangium, which in the 

 Lycopods is relatively small and simple, and has an undivided arche- 

 sporium. It is suggested that in this series there may be seen a 

 progression analogous to that by which the vascular plants originated 

 from some Bryophytic forms with simple sporogonial head. Take, 



