114 VASCULAR CRYPTOGAMS 



Fossil Vascular Cryptogams. 



Fossil remains or impressions of plants are found in all the stratified 

 geological formations from the Upper Silurian to the latest. Of the 

 Thallophytes that must certainly have existed in the seas from which 

 the oldest fossiliferous strata were deposited, the traces are, as might be 

 expected, few and doubtful ; and it is certain that many markings that 

 have been claimed under this category do not belong to the vegetable 

 kingdom at all. The remains of Vascular Cryptogams make their first 

 appearance in the Upper Silurian, and are remarkably abundant in 

 the Devonian and Carboniferous formations. During these periods 

 the arborescent vegetation of the globe consisted entirely of Vascular 

 Cryptogams and Gymnosperms, no remains that can be referred with 

 certainty to Angiosperms being known earlier than the Permian forma- 

 tion. The structure and mode of reproduction in Vascular Cryptogams 

 seem to have been remarkably uniform from the earliest times to the 

 present. The remains found in the fossil state belong, of course, ex- 

 clusively to the sporophyte generation ; but these indicate not only 

 that nearly every class of Vascular Cryptogams now in existence was 

 represented in the Carboniferous period, but also that none of the 

 primeval forms of vegetable life at present discovered presented charac- 

 ters differing very widely from existing types. 



Fossit RhizocarpejE. 



The fossil remains that can be referred, with any degree of cer- 

 tainty, to the RhizocarpeEe are very scanty. A few leaves found here 

 and there have been described by their discoverers, under the names 

 Marsilidium (Sclienk) and Sphenoglossum (Emm.), as representing genera 

 nearly allied to Marsilea ; and capsules presenting an external resem- 

 blance to the sporocarps of Pilularia and Marsilea have been found in 

 the Eocene. 



The Salviniaceae are represented with much more certainty in the 

 Miocene, impressions of leaves found in various beds belonoing to 

 that series being indistinguishable from those of Salvinia. More doubt 

 attends the identification of fructifications referred to this order. 

 Strasburger and Solms-Laubach think it possible that certain minute 

 echinate bodies found in calcareous nodules in the Carboniferous 

 described under the names Traquairia(Camith.), Zygosporites(Will.), and 

 Sporocarpon (Will.), the first of which is regarded by its discoverer as a 



