GOO 



SUPPLEMENT 



break, corgulate. and become a stiff jelly, it 

 seems probable there may be some circulation 

 which prevents the same effects in the vessels. 

 The sudden shrinking, 'closing, and opening 

 of flowers, the rising and sinking of the heads 

 of poppies, &c., the vermicular motions of the 

 veins of plants when exposed to the air, seem 

 also to imply somewhat like sensation. The 

 microscope may perhaps be of service to dis- 

 cover much more on these subjects than we 

 yet know. Mr Leeuwenhoeck tearing to 

 pieces a leaf of the species of box called Palma 

 cereris, that he might examine it the better, 

 computed one side of it to be furnished with 

 one hundred and seventy-two thousand and 

 ninety pores ; and as the other side must have 

 as many, (?) the whole number of pores in a 

 single leaf of box will be three hundred and 

 forty-four thousand, one hundred and eighty. 

 The leaves of rue seem full of holes, like a 

 honey-comb ; all the kinds of St John's wort 

 appear likewise struck full of pin-holes to the 

 naked eye ; but the microscope shows that the 

 places where those holes seem to be, are really 

 covered with an exceeding thin and white 

 membrane. The under side of the herb Mer- 

 cury, looks as if rough cast with silver, and the 

 ribs full of white round transparent balls, like 

 numberless grapes, fastened by slender foot- 

 stalks. A sage leaf appears like rug or shag, 

 full of knots, tasseled with silver thrums, and 

 embellished with fine round crystal beads or 

 pendants, fastened by little foot-stalks. The 

 under side of a rose leaf, but especially of 

 sweet-briar, looks diapered Avith silver." 



" Every body knows that the leaves of sting- 

 ing nettles are thick set with sharp prickles, 

 that penetrate the skin when touched, and 

 occasion pain, heat, and swelling . which 

 symptoms were imagined, formerly, to ensue 

 from the prickles being left in the wounds 

 they make. But the microscope discovers 

 something much more wonderful in this com- 

 mon vegetable, and shows that its prickles are 

 formed and act in the same manner as the 

 stings of living animals. For every one of 

 them is found to be a rigid, hollow body, ter- 

 minating in the most acute point imaginable, 

 with an opening near its end. At the bottom 

 of this cavity lies a minute vessel or bag, con- 

 taining a. limpid liquor, which, upon the least 

 touching of the prickles, is spirted through the 

 little outlet ; and, if it enters the skin, pro- 

 duces the mischief before mentioned by the 

 pungency of its salts. Hence it comes to pass, 

 that when the leaves of the nettles are consid- 

 erably dried by the heat of the sun, they sting- 

 but very little ; whereas such as are green 

 and juicy, produce violent pain and inflamma- 

 tion. But the quite contrary to this would 

 happen, if the symptoms were only owing to 

 the breaking of the prickles in the flesh : since 



when dry, they must be more brittle, as well 

 as more rigid, than when they abound with 

 ce." Our author concludes his remarks 

 3y suggesting this query : " Are there any 

 valves in the vessels of vegetables, as in those 

 of animals, to let the juices pass, but hinder 

 their return ?" To this inquiry we believe 

 no answer has yet been returned by any sub 

 sequent observer; it is scarcely necessary to 

 say that it is deserving of patient investiga- 

 tion. 



We must now briefly glance at the general 

 structure of those cryptogamian plants, whose 

 parts are too minute to be distinctly seen by 

 the naked eye. Of these plants there arc 

 four Orders: the Ferns, the Mosses, the 

 Algae, and the Fungi. 



The most remarkable features in the ferns, 

 namely, their seed-vessels and seeds, have al- 

 ready been noticed. The seed-vessels are 

 termed capsules, and are usually surrounded 

 by an elastic ring ; the seeds themselves are 

 named sporules. These are objects that re- 

 quire considerable magnifying power to de- 

 velope them. The leafy stem of the fern (the 

 frond) is an object of great interest when viewed 

 on the under side, which exhibits all the seed- 

 vessels arranged in regular dotted lines. 



The mosses are a numerous family of very 

 minute plants. " They are supposed to be 

 devoid of woody fibre and vascular tissue. 

 When a leaf is carefully examined, the septa 

 which divide the different cells that compose 

 it, will in many species be found to consist of 

 a single spiral line, taking a spiral course from 

 one end of the cell to another. To observe 

 this, it will be advisable previously to soak 

 the moss in water, in order to expand the cells. 

 In collecting mosses, it is essential to procure 

 them with the theca (before noticed and illus- 

 trated,) " as without it, it is very difficult to 

 determine the genera to which they belong." 

 Plate 35, fig. 37, is a leaf of sphac/num, more 

 usually known under the name of bog-moss. 

 By reflected light, and when laid on a dark- 

 coloured stage, it appears delicately white, 

 and the fibrous structure of the septa is readily 

 perceived. When viewed by transmitted 

 light, the regularly disposed hexagonal cells 

 present the appearance of delicate tracery, or 

 lattice work. It is here shown under the low 

 power of 100 on the surface. " Mosses of all 

 kinds are agreeable objects, and appear, by 

 the microscope, to be as perfect in their leaves, 

 flowers and seeds, as the largest plants or trees. 

 Those, particularly, that grow on the rocks 

 and coastsof the sea, exhibit amazingbeauties." 

 The order, named alyce, includes the lichens, 

 fuci, and confervae ; and those exceedingly 

 minute vegetations which compose the green 

 matter on unfrequented paths, and also the 

 various kinds of mouldiness, may be placed 



