PLATE XXII— MALE SHIELD FERN (Aspidium filix-mas). 



Ferns have always attracted notice from their graceful outlines and their varied forms, still it, is only comparatively recently that the 

 complete course of their life history has been made out The frond of the Fern is the most conspicuous, the underground portion 

 being generally overlooked Having so much leaf about them, they generally inhabit moist and shady situations. Their prevailing 

 colour is green, but towards the autumn a brown hue appears on the under surface of the frond, in streaks or patches, and this is due 

 to the formation of spore-cases containing the spores. 



The Male Shield Fern is so named by way of contrast to an allied form— the Lady Fern, with its graceful habit, its elegant form, 

 and its delicate hue. It bears its fronds in tufts, arranged in shuttle-cock fashion, and rising to a height of two or three feet. The 

 young fronds are rolled up like a shepherd's crook, and gradually unfold themselves. The veining of the leaflets is distinctly seen, and 

 that constant forking of the veins so characteristic of Ferns. The spore-cases are arranged in patches, each patch being indicated by 

 its kidney-shaped cover. The amount of spores produced is enormous, and readily accounts for its extensive distribution. Professor 

 Dodel-Port has reckoned the number of spores scattered by a single fern, in a single summer, to be no less than one thousand millions. 

 Fig. 1. Underground Stem ascends obliquely, and is completely covered with the stumps of leaves, from the base of which the 

 numerous roots arise. 



Fig. 2. Fertile leaf or frond bearing Sporangia on under surface. 



The leaf is bi-pinnate; the pinna? are long, narrow, tapering, and the pinnules are obtuse. 



On the under surface of the leaf, usually at the forking of two veins, kidney-shaped structures appear called 

 Indusia. Each Indusium covers a cluster of stalked capsules, such a cluster being called a Sorus, and each stalked 

 capsule a Sporangium.- 



Fig. 3. Pinna or leaflet on upper surface. 



The pinnules towards the top run into each other 

 The forked Venation is evident 



Fig. 4. Pinnule from base of Pinna. 



The Indusium may be found dosed over the cluster of Sporangia, or raised on one side to allow the ripe spores 

 to escape, or in some cases burst. 



Fig. 5. Section of Pinnule through Ripe Sorus in Fig. 4. 



Indusium arising from central swelling of vascular bundle, arching completely over clusters of Sporangia, and 

 consisting of a single layer of nucleated cells in its expanded portions. 



Sporangia in different stages of development, opened and unopened, full and empty of Spores. Some have 

 longer or shorter stalks, with a stalked gland which is peculiar to the species, and there are several hair-like unde- 

 veloped Sporangia known as Paraphyses. 

 Fig. 6. The Sporangia may be rubbed off on a slide and examined in water. They can afterwards be burst by pressure on the 

 cover-glass. 



The Sporangium is an oval body borne by a short stalk. There is a ring of thick projecting cells extending 

 from the cleft overhead, and backwards to the top of the stalk. The cells forming the slightly convex wall on 

 either side are thin and easily ruptured. 



Fig. 7. Spores. 



The Spore has a thick, outer brown coat or Exosporium with irregular markings, and a thin, inner delicate coat or 



Endosporium. 



