THE LASTREAS "т 
HYMENOPHYLLUM UNILATERALE (THE ONE-SIDED 
Епму Fern) (Plate XXXIX) 
Somewhat more common than H. Tun- 
bridgense, and occupying precisely similar 
habitats. The only differences, indeed, 
are indicated in the name, as regards form 
of frond (Fig. 145), and in the shape of 
the spore receptacles, which in this species 
consist also of two valves, but differ in 
shape, as shown in Fig. 145 ; otherwise our 
previous remarks apply exactly. 
Fig. 145. A. unilaterale 
(pinna and sporangium). 
THE LASTREAS (NEPHRODIUMS) (THE BUCKLER FERNS) 
The Lastreas are also named Nephrodiums, and the latter name 
being descriptive of the kidney-shaped spore cover of the genus, 
we think it well to mention it, since as a distinctive name it is 
better than a merely personal one. The latter, however, Газйса, 
named after a French botanist, is too familiar to dislodge from the 
British Fernist’s vocabulary, and we are the very last to attempt 
to do so and thus contribute to the confusion already caused in 
that connection by would-be reformers. As we have said, it is the 
kidney-shaped indusium, or spore cover, which distinguishes this 
genus, and this is indicated in the popular name of Buckler Ferns, 
as distinct from the Shield Ferns, in which the cover is perfectly 
round, This, however, is by no means the only difference, since 
the Shield Ferns are of very different make, and are all easily 
recognizable by the peculiar mitten-shaped pinne, or pinnules, 
as well as by their texture. 
There is considerable difference of opinion as to the number 
of our native species of this genus, owing to the fact that several 
of them run each other so close, and present so many linking or 
intermediate forms, as to render the drawing of a hard and fast 
line an impossibility. Several species, however, are beyond cavil, 
viz. L. montana (oreopteris), the Lemon-scented Fern, L. thelypteris, 
the Marsh Fern, L. dilatata, the Broad Buckler Fern, L. rigida, the 
Limestone Buckler Fern, and Г. emula, the Hay-scented Fern. 
These are accepted generally as unassailable species, though the 
late Mr. E. J. Lowe, in his British Ferns and Where Found, put 
forward the theory that L. emula was merely a mountain form of 
L. dilatata, to which it was apt to revert under unfavourable 
conditions, an idea which we cannot possibly accept, as there are 
marked specific differences. Another species, the commonest of all, 
L. filix-mas, or the Male Fern, we have not ranked with the un- 
assailables, since Mr. G. B. Wollaston discovered, and undoubtedly 
demonstrated, that this species fell into three sub-species, each with 


