84 MR. CHURCH ON THE FORM OF THE 
can confirm the general accuracy of Duval-Jouve's figures so far 
as they relate to species found in Britain. 
To discuss the difficult question of the nomenclature of these 
plants is beside my purpose; I shall therefore do no more than 
designate each form named by two or three of its best-known 
synonyms. At the same time, it seems that the results of such 
inquiries as the present, as possibly affording criteria of generic if 
not of specific difference, eannot be wholly disregarded, and may 
ultimately aid us in arriving at a more consistent classification 
for the Filices. 
The genera Polystichum and Lastrea as understood by Moore 
and many other authors are respectively coextensive (so far as. 
our native ferns are concerned) with the genera Aspidiwm and 
Nephrodium adopted by Hooker in his * British Ferns’ (1862). 
I have examined transverse sections of the stipes of all the gene- 
rally received species and many of the varieties included under 
these generie appellations, and in two species only did I find any 
material departure from that one particular arrangement of the 
vascular fasciculi which is disclosed by a transverse stipital section 
of such a form as Moore's Lastrea Filiz-mas or Polystichum Lon- 
chitis. In Nephrodium Filiz-mas, N. rigidum, N. cristatum, N. 
spinulosum a. bipinnatum, B. dilatatum, y. emulum, ò. dumetorum, 
Aspidium aculeatum a. lobatum, B. intermedium, y. angulare of 
Hooker, and also in the forms Lopkodium glandulosum, L. uligi- 
nosum, L. nanum, and L. collinum of Newman, the same disposi- 
tion of the vascular tissue occurs. The two notable exceptions to 
which I have before alluded are found in Nephrodium Thelypteris 
and JV. Oreopteris of Hooker, identical with the Lastrea T hely- 
pteris and L. montana of Moore and the Hemestheum Thelypteris 
and Lastrea (Hemestheum) montana of Newman. In fig. 1 the 
prevalent arrangement is shown; in fig. 2 that which occurs in 
the mountain fern; while fig. 3 represents that of the marsh fern, 
which I will now more particularly describe. In all cases the 
sections noticed are those of the stipes, not of the stem; and I 
have freely availed myself of the use of a very weak solution of 
perchloride of iron, in order that the tracts containing tannin 
might be distinctly marked out. 
Nephrodium Thelypteris, Hooker. 
Hemestheum Thelypteris, Newman. 
Lastrea Thelypteris, Moore. 
The present plant is not only closely connected in many of its 
