228 EVIDENCE FROM PALAEOPHYTOLOGY 



There are three palpable deficiencies in the Palaeontological evidence : 

 one, as has been said, is its incompleteness as regards the prime origins 

 of the leading types which are lower in the scale of vegetation ; another 

 is the usual, and almost necessary absence of developmental detail ; the 

 third arises from the frequency with which fossils are known by impressions 

 only, without the material sufficing for study of the internal structure. 

 This is especially so for some of the earliest, and from an evolutionary 

 point of view the most important forms. The first is by far the most 

 serious shortcoming. . 



The earliest fossil-bearing strata contain plant-remains which are more 

 in the nature of independent problems than an assistance, on any basis 

 of comparison, to the understanding of the known types of the vegetable 

 kingdom. Such plants as Nematophycus and Pachytheca suggest the 

 existence of Algae in the Silurian age, but are not readily ranked with 

 more modern forms. Similarly, the plant-remains from the Lower Old 

 Red Sandstone are highly problematical, though they indicate a probability 

 of terrestrial life. This seems more clear in the Middle Devonian, where 

 among other remains of plants apparently of the land, Palaeopitys Milleri 

 has been found : this is a stem with structure, showing tracheides arranged 

 evidently as having been produced from a cambium, while pits are seen 

 in the longitudinal sections : the whole structure is reminiscent of some 

 Cordaitean structure. But it is only in the upper Devonian that the 

 'remains of a Land-Flora are such as to be referable with any degree of 

 confidence to known types : thus Bothrodendron Kiltorchensc seems plainly 

 to be a large Lycopod ; Archaeopteris hibernica has usually been referred 

 to the Filicales, though it has recently been suggested that it may not 

 improbably be in reality the male fructification of a Pteridosperm ; 

 Pseudobornia ursina lately described from Bear Island by Nathorst, is a 

 Calamarian type with relatively large fimbriated leaves; characteristic 

 Cordaitean remains are also to be found. These may all be referred to 

 well-known groups of Land-growing Plants, and though they may differ 

 in certain important respects from related forms of later date, they show 

 in complexity of character, and often also in size, features which are 

 definitely those of the highly organised phyla to which they are referred. 

 Thus the early representatives give little clear information beyond the fact 

 of the early existence of those phyla to which they belong : they do not 

 provide an explanation of their origin, and help only slightly to form 

 opinions as to their mutual relations. Few facts are more striking than 

 this apparently sudden presentment of certain vegetable types, already 

 showing in a high degree the characteristics of their class. An extreme 

 case of this is pointed out by Zeiller. 1 He remarks that evidence of the 

 existence of the Gymnosperms, " dates from the base of the strata of Gaspe 

 in Canada; that is to say, from the most ancient epoch which has left to 

 us the remains of terrestrial plants : they are there represented by the 

 1 Elements de Palaeobotanique^ p. 369. 



