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 MWematophycus 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, Padacopitys Millert 
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 Kiltorchense 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 \ately 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 Zeiller1 He remarks that evidence of the 
existence of the Gymnosperms, “dates from the base of the strata of Gaspé 
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 
1Eléments de Palaeobotanigque, p. 369. 
