i37 
Hooker . — On P achy theca. 
no organic connection with the cortical, and as indeed belong- 
ing to an intruded parasitic alga, or the mycelium of a 
parasite — an opinion shared by several algologists. I could 
find no connection between these and the cortical portion, nor 
could Mr. Busk nor Dr. Lankester, who have both examined 
the specimens. 
The third point is the total absence of any point of attach- 
ment on the surface of the specimens, or of any indication even 
of such. Nor is there any indication in the arrangement of the 
tissues, of growth from a definite point. I have only further 
to remark under this head that no specimens showed any 
trace of organs of fructification. 
In 1883 Principal (now Sir William) Dawson communicated 
to the Geological Society of London ‘ Notes on Prototaxites 
and P achy theca discovered by Dr. Hicks in the Denbighshire 
Grits of Corwen, N. Wales/ I was then absent in Italy, but 
Mr. Dyer, having access to my sections of P achy theca , com- 
municated the latter to Mr. Judd, the President of the Society, 
for exhibition at the meeting, with a note to which I shall 
hereafter refer. 
At that meeting Sir J. W. Dawson expressed the opinion 
that P achy thee a was more probably a seed than a spore case, 
and that it has the structure of Aetheo testa , to which genus he 
had previously referred a similar seed found in the Devonian 
of Scotland. In another paper, he mentions similar bodies to 
P achy theca being found in a pyritised state in the Upper 
Silurian of New Brunswick, associated with the wood of 
Prototaxites ; and adds that these specimens ‘ though on the 
whole less perfectly preserved as to structure than the Welsh 
specimens, when sliced in certain directions they present 
traces of a micropyle and embryo, and are probably true 
seeds/ 
In still another paper Sir J. W. Dawson repeats his opinion 
as to there being little doubt that the New-Brunswick and 
Corwen specimens may be referred to Brongniart’s Aetheotesta : 
and he points out, as worthy of note, that Brongniart says of 
his Aetheotesta subglobosa from the Coal-measures, that the 
