Algce as Geological Guides, — James. 99 
can be detected. Whole fields of this ancient marine vegetation ap- 
pear like a grass plot, each blade of which has some peculiar feature, 
but none marked enough to make it positively distinct. Either there 
are as many species as individuals, or all belong to one species, repre- 
sented by a great number of closely allied varieties. They can not be 
used as geological guides." (pp. 100-101.) 
Count H. Solnis-Laubach* uses equally strong language 
when discussing Algae. Besides the genuine Algae, he says: 
"There still remain a large number of forms from all the formations, 
from the Quaternary back to the Lower Silurian, which have been de- 
scribed under an abundance of generic names; but they have virtually 
no interest to the botanist, because there is no immediate possibility of 
profitable comparison with known algal types. We may, perhaps, be 
able at some future time to pick out a type here and there [from] this 
hopeless chaos, but it is scarcely possible that we shall ever attain to a 
better position as regards the remainder. We must necessarily be 
always dependent on characters derived from external form, and these 
in the case of the Alga? prove only too little; we can scarcely hope to 
penetrate to the inner structure of the fructification, which can alone 
determine the affinity. And, to meet an objection which may be ex- 
pected from the paleontologists, I will add at once that I should not 
hesitate to say the same of the Conif eras, for instance, if we had nothing 
left of them but the impressions of the leaves; but there we are better 
off, for cones, wood and fragments showing anatomical structure have 
been preserved as so many points of support for the conclusions, by 
which we can be continually testing the degree of probability to be as- 
signed to the new conquests. What mistakes may be made without the 
aid of such objects is shown by the number of impressions of conifers, 
which are explained by older authors, by Brongniart for example, as 
Zonarites digitatus, various Caulerpita?, and other Alga?." 
The illustrious algologist, Harvey, gives similar testimony. 
Rogers, in the Geology of Pennsylvania,! refers to certain fos- 
sil remains found by him and supposed to be plants. They 
were sent to Prof. Balfour who wrote as follows in regard to 
one which presents many points of resemblance to the genus 
Dendrophycus, and which, notwithstanding the opinions of 
Newberry and others, I for one can not but regard as the im- 
print of drainage channels upon mud. Prof. Balfour says: 
•'On the whole subject of such fossil forms, I would take leave to for- 
ward to you the following words of Harvey, who in speaking of the sea- 
w r eed called Ptilota rhodocallis says: 'At first sight this beautiful 
species might almost be taken for Rhacelocarpus billardieri, ho similar 
are its ramifications and color ; but the structure of the frond and the 
*Fossil Botany. Translated by Garnsey and Balfour. London, L891, 
p. 45 et seq. 
tVol. ii, 1858, pp. 830 and 884. 
