Dr Marti us 0^1 Antediluvian Plants. 51' 
two to four long, which are disposed in a determinate order, 
differing in different species, and, as has been observed, only 
come into view after the pale« have disappeared. These diver ^ 
ticula are filled with a very fine ferruginous, powder, appearing 
under the microscope to 'consist of oblong or subangular, semi- 
transparent or opake ' bodies, covered with very slender hairs, 
and sticking together, and if I be not egregiously mistaken, are 
in some way subservient to the function of fructification. But, 
as I intend to treat in another place on this subject, as well as 
the internal structure of ferns, I need not prosecute it farther at 
present, what refers to the external characters being sufficient 
for our object. I shall only add, that the petiolar cicatrices 
shew various semicircles near the margin, and in the disk, which 
are the rudiments of fasciculi of vessels passing from the stem 
into the stipes, remaining under the form of warts and tubercles, 
after the petioles have been disengaged from their adhesion. 
After premising this much regarding the stems of ferns, the 
characters by which the arborescent JilicUes are to be described, 
are easily laid hold of, and may be applied to the specimens 
which occasionally come in our way, provided due attention be 
paid to the various modes in which they may present themselves, 
whether the specimens be actual petrifactions or casts. For it 
is properly observed by the celebrated Rhode that the ante- 
diluvian plants of our coal-mines occur in four different condi- 
tions, and these of the greatest importance for distinguishing the 
genera : some consist of vegetables converted into carbonaceous 
clay ( Kohlenschiefer or S chief erthon J, and still invested with 
their bark, reduced to the state of charcoal — others exhibit 
impressions of the same plant, with the surface entire, upon 
clay, slate, or sandstone — others are decorticated vegetables 
themselves ; — and, lastly, others are impressions of these decor- 
ticated plants. Before coming to any conclusion, therefore, 
with regard to a petrified fern, in order to determine to what 
sort of cast or petrifaction the specimen under examination is to 
he referred, it is necessary for this purpose that the characters 
which we derive from the entire specimen only, and not from 
its impression, be properly understood, and duly applied. 
* Beytfisge ^ur Pflanzenkunde der Vorwelt ,* Breslau, 1820, fol. 
D S 
