THE COMMON PRICKLY SHIELD FERN. 127 
(1) P. aculeatum is stouter, more erect, and altogether more rigid 
in texture; while P. angulare is normally lax and more herbaceous, 
and equally large or even larger in size. 
(2) P. aculeatum has its pinnules either confluent or decurrent, 
(in which cases there is no difficulty whatever in distinguishing it), 
or, when the pinnules are distinct, as in the most perfect plants, 
they are wedged-shape at the base, the anterior side being truncate, 
and the posterior obliquely incised in straight lines, the two lines 
describing an acute angle by the apex of which they are attached 
to the rachis; while in P. angulare the truncated anterior base is 
more curved in outline, and the two lines of the base describe a 
right angle or an obtuse angle, at the apex of which is a distinct 
slender petiole, by which they are attached. 
(3) P. aculeatum has its sori medial, that is, attached at a point 
along the middle part of the venule, the apex of which is carried 
out to the margin of the pinnule, the sori thus bemg placed nearer 
the base of the venule than its apex, i. e., nearer the point of fur- 
eation; while in P. angulare the fertile venule stops about midway 
across the pinnule, and the sorus is commonly placed at or almost 
close to its apex. These peculiarities observed in connection with 
each other will serve to reduce the dubious forms within very 
narrow limits indeed, at least so far as British examples are con- 
cerned. The portion rather below the middle of the frond and 
- the basal pinnules should be taken for examination. 
This is one of the most easily cultivated of all the larger hardy 
Ferns. It prefers a loamy soil and partial shade ; and is increased 
readily by division. Being evergreen, its varieties are among the 
most desirable of our native species for the decoration of shady walks 
and rockeries, in which latter situation especially, where the roots 
are generally well drained, provided the plants are not exposed to 
the effects of severe drought and are moderately shaded, they 
thrive admirably. It is also very manageable as a pot plant, and 
under any circumstances is ornamental in its character. The 
smaller form, known as /obatwm, is perhaps the most suitable for 
pot culture, on account of its size and the elegance of its fronds, 
which not uncommonly assume a very graceful lateral curve. The 

