Sporangia borne on elevated receptacles, forming roundish sori imperfectly covered by very delicate hood-shaped indusia attached to the base of the receptacles.
The indusia appear as little whitish scales on the back of the veins.
To this it may be added, that in some of the areoles the two sori meet and are confluent at the outer angle of the areole; and in this case the two indusia are sometimes, though not always, united into one.
The indusia of the areoles next the midrib are also often bent at an angle, and the two portions plainly united.
The indusia are larger than in most of the related species, flat, perfectly smooth, orbicular with a very narrow sinus, and slightly erose-crenulate on the margin.
The indusiaare very delicate; and the free edge is directed toward the middle of the lobe, excepting the indusia of the sori nearest the midrib, and these open toward the midrib.
In systematic botanies the indusia play an important part in determining genera.
As these indusia can be seen satisfactorily only by the aid of a magnifying-glass, there is frequently some difficulty in distinguishing this variety.
Although the genus Polýstichum represents the true shield ferns, the wood ferns are also thus designated, as their indusia have nearly the shape of small, roundish shields.
Pinnules toothed or entire nearly covered beneath with the large, thin, imbricated indusia which are orbicular with a narrow sinus, having the margins ragged and sparingly glanduliferous.
In the east it is often dwarfed--six to ten inches high, growing in tufts with stout rootstocks, having the pinnules finely toothed instead of rounded and the indusia often lunate, rarely twice as long as broad.
These are disposed on both sides of the mid-ribs of the lobes; they are circular in shape and have no indusia or covering of any kind.
With the disappearance of the indusia the sori tend to spread over the whole surface of the back of the frond.
The clusters of the sporangia are covered with small indusia which are slightly notched.
These have the same curious dividedindusia to be observed in the Alpine Woodsia.
In their early days these clusters are distinctly in the form of lines, but after the throwing off of the indusia they rapidly mature and spread to such an extent that the whole of the under-surface of the pinnule is covered.
The indusia are soon thrown off when the spore cases start to develop.
This species is very distinct in its general appearance from the Holly Fern, though it can at once be seen to be a Shield Fern by the unnotched indusiawhich cover the sori.
The pairs of sori are covered with pairs of indusia which, on the maturity of the sporangia, open out opposite to each other.
After the falling away of the indusia the sori tend to spread, so that they may finally cover almost the whole of the back of the fertile pinnae.
The sori are very freely scattered on the lobes or pinnules at the back of the frond, and these are covered with the curious hooded indusia which were noticed in the last species.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "indusia" in a variety of sentences. We hope that you will now be able to make sentences using this word.
