ON MICROSCOPIC DISCOVERY, 



599 



posit it with the plume upwards ! The only 

 other appendage to which we shall refer, is 

 the a/a, or wing, a line membrane attached 

 either to the back or margin of certain seeds. 

 On a microscopic examination, this does not 

 appear to be intended so much for a means of 

 transit, as for absorbing nutriment to facilitate 

 the germination of the seed. It is, in most 

 instances, a layer or reticulation of capillary 

 tubes, protected by a double membrane. 



The conformation of poppy seeds is exceed- 

 ingly curious. In outline they somewhat re- 

 semble a kidney, and their surfaces are divided 

 into angular compartments, by means of re- 

 ticulated fibres connected by an exceedingly 

 thin and transparent membrane. Plate 34, 

 fig. 29, is the seed of the Calampelus Scaber, 

 in which the ala, or wing, is a characteristic 

 feature ; the external tunic, or outer integu- 

 ment of the seed, is also worthy of observa- 

 tion. Fig. 30, represents a seed of the French 

 Marygold ; and in this we notice the wing- 

 like disposition of the down before adverted 

 to. Had the object been sufficiently magni- 

 fied, this down would have exhibited the char- 

 acter of fig. 9. It is barbed, or spinated ; 

 and whilst it serves as a vehicle for the transit 

 of the seed, it also controls its position when 

 placed in the earth, as previously stated. Fig. 

 42, exhibits the Theca, or seed vessel of Moss, 

 under a superficial magnifying power of 100. 

 Without the aid of the microscope, the fructi- 

 fication of the mosses could never have been 

 understood. Botanists are now enabled to 

 distinguish the various genera, by observing 

 ihe character of the fringe round the mouth of 

 /he seed-vessel, and the peculiarities of figure 

 in the seed itself. The powder, or seed, of 

 Puff-ball, a species of Fungus, is an object of 

 great interest, under a high magnifying power. 

 Baker describes it in these words : " The 

 seed of the Puff-ball seems to the naked eye 

 like a smoke or vapour ; but when examined 

 by one of the greatest magnifiers (for else it 

 cannot be distinguished) it appears to be in- 

 finite numbers of little globules, of an orange 

 colour, somewhat transparent, whose axis is 

 not above the fiftieth part of the diameter of a 

 hair : so that a cube of a hair's-breadth diame- 

 ter, would be equal to an hundred and twenty-- 

 five thousand of them." The same author's 

 remarks on the seed-vessels of ferns, the 

 second order of Cryptogamian plants, agree 

 with recent observations. " The ancients," 

 he says, " imagined the capillary plants and 

 many other kinds to produce no seeds at all, 

 but the microscope has discovered that all the 

 several species of fern are so far from being 

 barren in this respect, that they are amazingly 

 fruitful : that the seed-vessels are on the backs i 

 of the leaves, and that the dust which flies off I 

 when we meddle with them, is nothing but | 



their minute seeds. These seed-vessels appear 

 to the naked eye like a black or brown scurf 

 on the back side of the leaf ; but, when viewed 

 by the microscope, resemble little circular 

 tubes, divided into many cells, containing seeds. 

 When the seed is ripe, the vessels fly open 

 with a spring, and spirt the seeds out on every 

 side, in the form of dust : and if at that season 

 some of the leaves are put in a paper cone, 

 and that be held to the ear, the seed-vessels 

 may be heard to burst with a considerable 

 noise. Some of these minute vessels contain 

 at least one hundred seeds, invisible to the 

 naked eye. Fig. 33, shows the pod and seed 

 of a kind of fern, named polypodium, that 

 vegetates on the bark of the oak. The seeds 

 contained in each pod correspond in number 

 to the divisions on its circumference. The 

 figures exhibit all the details observed under 

 a superficial magnifying power of 40,000." 



The plant, or tree leaves, require to be 

 considered distinctly from the petals of the 

 blossom ; for though the two have some things 

 in common, the latter affect the flower only, 

 whilst the former are organs on which the 

 health and vitality of the whole vegetable 

 structure principally depends. We have al- 

 ready adverted to the cuticle, stomata, and 

 absorbent vessels, and the important offices 

 they fulfil ; the other points of microscopic 

 interest are included in the following observa- 

 tions by Blumenbach. " The leaves are es- 

 sentially the same in composition with the 

 trunk and branches, inasmuch as it is possible 

 to distinguish in them cuticle, bark, woody 

 substance and medullary cellular structure. 

 The latter occupies the middle of the leaf, be- 

 tween the two reticular layers of woody sub- 

 stance, from which the other parts may be 

 removed by corrosion and similar processes, 

 leaving a skeleton leaf, as it is called. This 

 reticular woody substance is covered on both 

 sides of the leaf with a peculiar membrane, 

 generally called cuticle, but differing mater- 

 ially from the proper cuticle already men- 

 tioned, (which is really expanded over the 

 outer surface of the leaves,) and penetrated by 

 numerous absorbing vessels." 



We extract some interesting remarks con- 

 cerning leaves, from an author before quoted ; * 

 and the reader will admire the acuteness with 

 which he has anticipated the comparatively 

 recent discovery of the ct/clcsis, or circulation 

 in plants. 



" The leaves of trees or plants are full of 

 innumerable veins arid ramifications, that con- 

 vey the perspirable juices to the pores, for 

 their discharge. Whether or no there be any 

 circulation in them is still a matter of doubt ; 

 but as their juices, when let out, immediately 



* Baker. The Microscope made Easy, p. 246". 



