542 BOTANY pakt ii 



these may be briefly characterised as fern-like spermaphyta. They have shown 

 that the seeds of Lagcnostoma Lomaxi, Will, belong to Lyginodcndron, one of 

 the Cycadofilices with fern-like foliage, and that this plant must therefore be 

 placed in the Pteridospermeae. It is highly probable from the further work of 

 Scott (-''') that the whole of the Lyginopterideae and the Medulloseae must be 

 placed in this group. The structure of the seed of Lagenostoma, the best known 

 example of the new order, resembles that of Cycas, but, instead of the single thick 

 integument of the latter, had a cupular investment to the seed, on the outside of 

 the integument. In all Pteridospermeae the macrosporophylls resembled the 

 vegetative leaves almost exactly. The same is the case for the microsporophylls, 

 and their sporangia can hardly be distinguished from those of certain Ferns. In 

 the structure of the stems and leaves the Pteridospermeae are intermediate between 

 Ferns and Gymnosperms but nearer to the former group. 



Cordaites is a peculiar type confined to the Palaeozoic rocks. Owing to the 

 excellence of the preservation of their remains tlie morphology of the Cordaiteae 

 is as well known as that of the existing Gymnosperms. They were lofty trees with 

 linear or broad and lobed leaves. Their flowers diff"er considerably from those 

 of recent Gymnosperms. An important fact as bearing on the phylogeny of the 

 group is the presence of a male prothallus as a small multicellular body. The 

 ovules and seeds show great structural agreement with those of the Cycadaceae. 

 With the exception of some less common fossils {Cycuditcs, Dicranoithyllum),, 

 which may be placed with the Ginkgoineae, Cordaites is the most richly represented 

 type of Gymnosperm found in the Carboniferous rocks. Undoubted Gycadophyta 

 make their appearance in the lower Rothliegende. In later strata the geims 

 Walchia, of uncertain aSinity, appears ; the vegetative organs, which alone are 

 known, recall the lowest Coniferae (Araucariaceae). In the upper Rothliegende 

 undoubted Ginkgoaceae (Baiera) make their appearance, with another type referred 

 to the Coniferae {Ullmannia). 



The Cordaiteae disappear in the lower mesozoic strata. The Gymnosperm 

 flora can be followed through the Trias, in which it consisted of extinct types 

 of Gycadophyta, Ginkgoineae, and Coniferae {Voltzia, in the Bunter Sand- 

 stone), to the Jurassic period. In the latter it attained a great development 

 in that both the Ginkgoineae and the Cycadineae attained their maximum 

 development. 



Scott (-''=) has recently given an account of the appearance and the high degree 

 of organisation attained by the mesozoic Gycadophyta, from the knowledge obtained 

 by Wieland's study of the abundant material found in North America. The name 

 Cycadeoidea proposed by the American author is synonymous with Bcnncttites ; 

 fruits derived from the hermaphrodite flowers were already imperfectly known 

 from European strata under the latter name. The short and sometimes branched 

 stems resembled recent Cycads in their appearance and foliage and boi'c flowers 

 which were hermaphrodite and 12 cm. in length. A hundred or more spirally 

 arranged perianth leaves surrounded a whorl of 18-20 microsporophjdls, which were 

 united at the base to form a deep cup in the centre of which the gynaeceum arose 

 (Fig. 514). The pinnate microsporo])hj'lls, 10 cm. in length, resemble the leaves 

 of Ferns, and the microsporangia resemble the sporangia of the Marattiaceae. The 

 gynaeceum consists of numerous, long-stalked, atroi)Ous ovules which are surrounded 

 and separated by scale-leaves : tlie microsporopliylls, however, open freely on the 

 exterior. The ripe seeds contained a highly developed dicotyledonous embryo 

 and had no endosperm. They were protected and enclosed by the closely crowded 

 outer ends of the scale -leaves. Just as the palaeozoic Pteridospernis combine 



