506 PHILOSOPHICAL TRANSACTIONS. [aNNO 174). 



and gives a pretty just description of the seed-vessels, and the manner in which 

 they grow, and intended a delineation of the figures. Swaminerdam perhaps 

 spoke what he thought to be true; and possibly he might have made the disco- 

 very many years before the time when he showed the seeds to the professor. 

 However, I am humbly confident of this, after numberless trials made with all 

 kinds of microscopes, and in all positions, and with different lights, that Swam- 

 merdam's account is just and accurate, in every point. I have viewed the se- 

 veral kinds of fern, English maidenhair, other sorts of maidenhair, wall- rue, 

 harts-tongue, and find the seed-vessels of the same form in all, some little dif- 

 ference being between some of them in the size only; and in the manner of 

 their being inserted on the back of the leaf, with the numbers in various plants, 

 there is a more considerable difference. Where there are fewer seeds, there are 

 more of a sort of fungus, or tubercle, very like what is called Jews-ears, which 

 seems to me designed to shelter the seed, which grow, as under covert, round 

 about them. 



In the female fern, and English maidenhair, the whole surface of the leaf on 

 the inside seems covered: so that the seeds guard each other in some measure; 

 though in these, after the seed-vessels are shook off, small membranes are found 

 hereand-there on the surface, a little curled, looking as if they had been raised 

 with the edge of a sharp pen-knife, from the skin of the leaf, not altogether 

 unlike the pieces of skin we are wont to raise in trying a pen-knife on one's 

 hand. 



The plant here attempted, as exhibited in %, f), pi. 10, with its seed-vessels, 

 &c. is the filix mas Dodonaei ; on the inside of the leaves of which are usually 

 seen several spots placed in a regular manner, of a light-brown or russet-colour. 

 In this plant the principal part of these spots is the fungus beforementioned, 

 around which the seed-vessels are inserted. 



The seed-vessels consist of a stalk, by which they are inserted into the leaf, 

 as cc, fig. 7, of a springy ribbed chord ee, having a great number of annular 

 ribs, exactly resembling the annular cartilages in the aspera arteria; and I know 

 nothing in nature so aptly resembling this chord, as the aspera arteria of a 

 small bird, as a robin or nightingale, &c. This chord incircles the globular 

 membraneous pod, where the seed lies, adhering to it, and dividing it into 

 two hemispheres. The pod ff is, in appearance, composed of a fine whitish 

 membrane, somewhat like that which lines the inside of a pea-shell. . The seeds, 

 fig. 8, k, are irregular in shape, and in their surface a little resembling a sort 

 of net- work. 



In viewing this admirable production of divine wisdom in this plant, I use a 

 single lens, and no deep magnifier, that I may have the advantage of the light 



