THE LADY FERN. 15 
curved semilunate or hook-topped sorus, or sometimes also returns 
along the posterior side of the venule and forms a short hippo- 
crepiform or horse-shoe-shaped sorus. In the more divided examples, 
this short equally-curved form of sorus is more frequent, and some- 
times in the very much divided fronds it is even more abundant 
than the simple oblong or semilunate form. In this latter state, 
the fructification might at a cursory glance be mistaken for that of 
Lastrea. The sori are at first distinct, but generally become more or 
less confluent by the spreading of the crowded spore-cases. Indusium 
membranaceous, variable in outline according to the form taken by 
the sorus, the free margin cut into capillary segments, and eventually 
becoming “repressed” or held back by the crowded mass of spore- 
cases. Spore-cases numerous, dark brown, obovate. Spores oblong, 
granulate or muriculate. 
Duration. The caudex is perennial The fronds are annual, 
appearing about May, and being destroyed by the first frosts, 
decaying early in the autumn even when protected against frost. 
This plant is the type of the genus Athyrium as here understood, 
consisting of asplenioid ferns, in which the sorus returns more or 
less on the posterior side of the receptacular vein, and becomes 
hooked or hippocrepiform, the attachment of the indusium being as 
in the Aspleniew along the side of the vein. 
The Lady Fern is not easily confounded with any other British 
species. Though related to Asplenium, and referred to that genus 
by many talented botanists, it is at once distinguished from all the 
British Aspleniums by its herbaceous texture, its annual fronds, and 
its whole habit, as well as by the curved or arcuate sori. On the 
other hand, these curved or hippocrepiform sori connect it in some 
degree with Lastrea, and it was no doubt the examination of specimens 
with advanced fructifications of this form which led to its being 
associated, as it was formerly, with Aspidium. The plant is not, 
however, sufficiently like any native species of Lastrea to be mistaken 
for one of them. 
The Lady Fern is a common and generally distributed species, 
attaining its greatest degree of luxuriance in damp, shady, and 

