342 Br. D. R. Scott [May 15, 



2. The arrangement of the pollen-sacs in groups on the under- 

 side of the cone-scales, like that of the spore-sacs of Ferns on the 

 under-side of the leaves. 



3. The carpels or fertile leaves of Cycas, which, though bear- 

 ing true seeds, are more like fertile Fern-fronds than any other 

 reproductive leaves. 



By themselves these characters, though suggestive, would be 

 inconclusive ; the anatomy is not directly comparable with that of 

 any living Ferns. 



What, then, do we know of the history of this family in past 

 times ? The Cycads are now a small isolated group ; in the Mesozoic 

 period, from the Trias to the Lower Cretaceous, they were one of the 

 dominant types of vegetation, and spread all over the world. Of the 

 fossil species recorded from the Oolite of the Yorkshire coast, and 

 from the Wealden of the South of England, one-third are referred to 

 Cycads, and they were equally abundant in the Mesozoic Floras of 

 North America, India and other countries. If they existed in the 

 same proportion now as then, they would have about 35,000 species 

 instead of 70! The Cycads of the Mesozoic, however, were not, as 

 now, a single family, but a great class (the Cycadophyta of Nathorst) 

 embracing very diverse types, often with organs of reproduction 

 widely different from those of their surviving relatives, and showing 

 a certain parallelism with angiospermous fructifications. But with 

 all this there vvas on the whole a remarkable uniformity in habit, 

 just as we find a general similarity in outward characters among so 

 many Dicotyledonous trees of the present day though belonging to the 

 most diverse families. In the Mesozoic rocks we also fi^nd a certain 

 number of plants (known only from their foliage) as to which it 

 remains doubtful whether they belonged to Cycads or Ferns, or to 

 some intermediate group. 



Besides the Cycadophyta, seed-plants were represented in Meso- 

 zoic days by a great number of Coniferae, more or less allied to those 

 still living, and by various forms akin to the Maidenhair-tree, 

 perhaps the most ancient type surviving in the recent Flora. 



When we go further back, to the Palaeozoic rocks, it is only in 

 their uppermost strata that we find forms clearly referable to Cycads 

 or Conifers. 



The best known seed-bearing plants of the older rocks are those 

 of the family Cordaiteie, which stretches back to the Devonian. 

 They were tall, branched trees, bearing great simple leaves, sometimes 

 a yard long. The anatomy of stem and root resembled that of an 

 Araucarian Conifer, but the leaves had just the structure of the 

 leaflets of a Cycad. Male and female flowers were borne in little 

 spikes or catkins, and may best be compared with those of the 

 Maidenhair-tree. The seeds, of which the structure is known, closely 

 resemble those of that plant, or of recent Cycads. 



The Cordaiteae, however, ancient as they are, were already pro- 

 nounced gymnospermous seed-plants; by themselves they give no 



