172 
the later portions of which we are abruptly 
confronted with algze of gigantic dimensions 
and a high degree of organization, thereby 
implying the existence of a long line of an- 
cestors in the earlier geological periods, of 
which all traces seem to have disappeared. 
Passing into the Devonian, such types gain 
greater prominence in point of numbers, 
and thence on to the present the successive 
formations give evidence of the continuous 
development of this type of plant life; and 
while in Nematophycus, Chondrites, Lagy- 
nophora and Bacillus we find well-devel- 
oped representatives of types known at the 
present time, their ancestral forms are to be 
sought in the Laurentian and portions of 
the early Paleozoic, where the only evidence 
of their former existence is to be found in 
the abundance of graphite and other forms 
of carbon. The most perishable of all 
plants, the Thallophytes, readily yield to 
that decay which is the invariable antece- 
dent of petrifaction, and the slight residue 
of structure which might remain is com- 
monly obliterated in the further metamor- 
phosis of the rocks in which they are held. 
It is therefore altogether exceptional that 
such plants should be preserved in recog- 
nizable form, and their value for phyloge- 
netic purposes, although very limited, ac- 
quires an unusual interest and importance. 
This is eminently true of the very plants 
through which the line of direct descent 
passes, since the green alge are, of all the 
group, among the most perishable. For 
these reasons it isin no way surprising that 
additional representatives of the Thallo- 
phytes among fossil plants are rare, that 
such plants as are found add but little to 
our knowledge of descent, and that they fail 
completely to illumine the line directly an- 
cestral to the Bryophytes—the evidence so 
far accumulated bearing altogether upon 
side lines represented by relatively durable 
remains. 
Among the higher Thallophytes, a few 
SCIENCE. 
(N.S. Von. XIII. No. 318. 
additions have been made to the Charo- 
phyceae by the recognition of the char- 
acteristic fruits in the Lower Tertiary of 
Wales, Ohio, where two species—C. Stan- 
ton and C. compressa of Knowlton are 
found. Fruit-like bodies having the exter- 
nal characteristics of Chara have also been 
observed in the Devonian at the falls of the 
Ohio, thus giving to this group of plants 
the possibility of a very ancient lineage 
which is justified on theoretical grounds. 
The very fragmentary remains so far 
known, the preservation of which depends 
upon their calcareous investment, neverthe- 
less serve to throw no additional light upon 
previous knowledge. Migula has suggested 
that these plants occupy a position superior 
to the Thallophytes as a whole and co- 
ordinate with the other great divisions of 
the plant world. This view has been 
adopted by Seward in his most recent con- 
tribution to paleobotany, and Campbell 
also regards it as deserving recognition. 
To the solution of this question, however, 
the fossil representatives contribute no 
information not derivable from existing 
species. 
Among the Phaeophyceae considerable 
interest has attached for a number of years, 
to a remarkable fossil originally described 
by Dawson as Prototaxites under the im- 
pression that it represented a primitive 
Gymnosperm allied to the Taxaceae. This 
view was disputed by Carruthers, who was 
the first to determine the algoid nature of 
the organism, and he assigned to it the 
name Nematophycus. Subsequent investiga- 
tions of North American material amply 
justified this view, and Dawson was led to 
so far modify his original opinion as to em- 
ploy the name Nematophyton. Several pro- 
visional species from the Silurian and De- 
vonian of America have been recorded, and 
to these there have been added three species 
from the same formations in Hurope. Car- 
ruthers has been led to suggest a possible 
