56 PTERIDOSPERMEAE [CH. 



was the first to recognise as the megaspore-bearing organ of 

 Lyginopteris oldhamia. Its structure has been thoroughly described 

 by Oliver and Scott 1 and these authors contribute a judicial 

 summary of the evidence on which Lagenostoma and Lyginopteris 

 are believed to stand for one and the same plant. The evidence 

 is based chiefly on the following considerations : an agreement 

 in the structure of the vascular bundles in the investments of the 

 seed with those in the leaves of Lyginopteris ; the presence in 

 the outer envelope of the seed of stalked glands identical with 

 those on the stems and petioles. The evidence does not as yet 

 amount to absolute proof, as the seeds, which occur either with 

 or without a stalk, have not been found attached to a Lyginopteris 

 frond. But ' where vegetative and reproductive organs presenting 

 identical structural features, not known to occur in other plants, 

 are thus found in close and constant association, the inference 

 that the one belonged to the other appears irresistible.' While 

 most botanists believe that a satisfactory case is established there 

 are a few 2 who refuse to believe in a connexion between Lagenostoma 

 and Lyginopteris until an actual union has been demonstrated. 

 The discovery by Kidston 3 of seeds attached to pinnae bearing 

 Neuropteris pinnules and the demonstration of organic continuity 

 between seeds and the pinnules of other Palaeozoic fern-like 

 fronds supply abundant confirmatory evidence that leaves no 

 doubt as to the occurrence of seeds on modified pinnae of Sphenop- 

 teris Hoeninghausi and of other closely allied fronds which represent 

 the foliage of different forms of Lyginopteris. In this connexion 

 it is pertinent to add that Grand'Eury 4 has found seeds of the 

 Lagenostoma type in close association with impressions of Sphenop- 

 teris Dubuissonis and other leaves of similar habit. 



A seed of Lagenostoma Lomaxi reaches a length of 5-5 mm. 

 with a maximum diameter of 4-4 mm. ; it is broadly oval or barrel- 

 like (fig. 408, C) and when immature was invested by a loose 

 irregularly lobed glandular envelope (fig. 408, B) from which the 

 seed eventually freed itself by a natural process of abscission. The 

 central body or nucellus, except in the apical region, is concrescent 

 with a fairly stout integument or testa (fig. 408, C, /) the outer 



1 Oliver and Scott (03) ; (04). 2 Horich (06) p. 48. 



3 Kidston (05 2 ) B. 4 Grand'Eury (05 2 ) B. 



