GENERAL RELATIONS OF PLANTS TO TIME. 435 



dubious exceptions, are not at present known to occur in 

 deposits older than the Upper Cretaceous, and hence would 

 seem to be a modern type. That they are, at any rate, much 

 more modern than the Gymnosperms may be safely con- 

 cluded, though it may be at the same time taken for granted 

 that we are still very imperfectly acquainted with their 

 geological history, since their first recorded appearance 

 presents us, not merely with a few sporadic precursors of the 

 group, but with a large series of sharply-differentiated and 

 well-known types. Lastly, the Monocotyledons are known 

 to occur as early as the Carboniferous, the Fothocites of the 

 Coal-measures being apparently the spadix of a plant alKed 

 to the existing Arums. 



Taking, in the next place, a brief historical retrospect of 

 the distribution of plants in past time, we find that the 

 oldest remains of vegetables (if truly of this nature) as yet 

 known, are the curious fossils of the Lower Cambrian 

 (" Fucoidal Sandstone ") of Sweden, to which the name of 

 Eophyton has been given. The precise affinities of Eophyton 

 are, however, uncertain, and it cannot even be regarded as 

 being beyond question that it is really referable to the 

 vegetable kingdom. The Lower Silurian rocks, on the other 

 hand, have been long known to yield remains which may be 

 looked upon as incontestably of a vegetable nature, and 

 which are almost certainly Sea-weeds. In addition to these. 

 Professor Lesquereux has recently announced the discovery 

 in strata of this age of fossils which he regards as an early 

 type of the great Palgeozoic family of the Sigillarioids {Pro- 

 tostigma sigillarioides). In the Upper Silurian have been 

 detected numerous Sea-weeds, and also remains of unques- 

 tionable land-plants. Among the latter, the Zycopodiacece 

 are represented by the singular spore-cases known by the 

 name of Pachytheca, by the familiar Palaeozoic genus Lepido- 

 dendron, and by the remarkable generalised type Psilophyton, 

 which is in some respects intermediate between the true 

 Club-mosses and the Ferns. Unquestionable Ferns {Eopteris), 

 allied to the Devonian and Carboniferous genus Neuropteris, 

 are present ; and the group of the Calamites among the 

 Equisetacece is represented by Splunoyhyllum and Annularia. 



