ON MICROSCOPIC DISCOVERY. 



597 



detected between them, of such a nature as to 

 keep up a circulation of fluids, such as is 

 found in all red-blooded, and so many white- 

 blooded animals." Most probably what is 

 termed 'the circulation in plants is nothing 

 more than the nutritive juices proceeding 

 through capillary vessels to all parts of the 

 plants, whence they do not return. The 

 reader may, however, choose to hear Mr 

 Pritchard's remarks on this subject, the more 

 particularly as they are the result of careful 

 observation with the finest instruments that 

 can be constructed. " The circulation in 

 plants, termed ci/closis, is a revolution of the 

 fluid contained in each cellule, and is dis- 

 tinct from those surrounding it. It can be 

 observed in all plants in which the circu- 

 lating fluid contains particles of a different 

 refra tive power or intensity, and the cellules 

 are of sufficient size and transparency. Hence 

 alt lactescent plants, or those having a milky 

 juice, with the other conditions, exhibit this 

 phenomenon. The following aquatic plants 

 are generally transparent enough to show the 

 circulation in every part of them : Nitella 

 Hyalina, Nitella translucens, Chara vulgaris, 

 and Caulinia frigalis. In the Frog-bit 

 (Hydrocharis) it is best seen in the stipules of 

 the leaves and the ends of the roots. The 

 magnifying powers suited for the above are 

 between 100 and 250 times linear. In the 

 Spider-wort (Tradescantia virginica) it is 

 seen in the filaments surrounding the stamens 

 of the flowers: power required, 300 to 500 

 times linear. In the common groundsel 

 (Senecio vulgaris) it is said to be seen in the 

 hairs surrounding the stalks and flowers." 



The respiration of plants is another feature 

 in which we trace-a similarity between vege- 

 table and animal bodies. The leaves in 

 plants answer the same purpose as the lungs 

 in animals, " for the execution of the phlogis- 

 tic process, which in the latter, is effected 

 principally by the inspiration of the respira- 

 ble part of the air on its basis, oxygen ; and 

 which, in plants, is performed almost exclu- 

 sively by the leaves. In plants also, this re- 

 spirable gas, or its basis, is, as in animals, 

 indispensable to the support of life; particu- 

 larly as Ingen-Housz's experiments have 

 rendered probable, for the purpose of prepar- 

 ing in their vital laboratory their principal 

 material of nutrition, carbonic acid, the excess 

 of which they subsequently exhale in the form 

 of carbonic acid gas. This important process 

 is carried on in its greatest activity in the 

 dark. During the day-time, on the contrary, 

 and particularly in sun-shine, it is much 

 more languid : hence at such time, plants 

 prepare and consume carbonic acid in smaller 

 quantities ; and, on the contrary, evolve 

 oxygen, the respirable part of the atmosphere, 



from their leaves." By the assistance of the 

 microscope we discover, in the cuticle on the 

 under side of the leaves, a number of small 

 openings, termed stomata, which are considered 

 subservient to the respiration of plants, as well 

 as to the exhalation of the fluids which are 

 evaporated from them in considerable quantities. 

 It is worthy of remark with reference to the 

 evaporation of moisture, that this process is as 

 necessary to vegetable, as that of perspiration 

 is to animal life ; for if the stomata of the leaf 

 be closed up artificially, or otherwise, the 

 plant, or that immediate part of it, becomes 

 diseased and withers. The alternate exhala- 

 tion of oxygen and carbonic acid gas from the 

 leaves of plants, must appear a remarkable 

 provision, subservient to the health and comfort 

 of man. During the day, when mankind are 

 in activity and requiring a full supply of re- 

 spirable air, the plants, in place of taking 

 from, add to its healthy qualities ; and when, 

 at night, the human race are wrapt in slum- 

 bers, and the functions of the animal body are 

 performed with less activity, and when conse- 

 quently less oxygen is required to carry them 

 on, the plants, in turn, take in their supply of 

 this gas, evolving it again with the morning 

 light for the benefit of the awakening world. 



Let us notice a few of the interesting facts 

 ascertained from a microscopic examination ot 

 a flower. We will begin with the petals, or 

 leaves, which surround and protect the repro- 

 ductive organs of the vegetable, arid constitute 

 the largest portion of the flower. The upper 

 and under surface of these are first to be ex- 

 amined, and the disposition of the downy 

 covering, or spines, or other remarkable fea- 

 tures, carefully noted. If then we are able to 

 separate the cuticle on the under side, it will 

 discover to us the stomata ; and the removal 

 of the cuticle exposes the absorbents of the 

 petal, whose use is to absorb the elements of 

 vegetable nutrition from the atmosphere. 

 Strip off the remaining petals from the flower, 

 and leave only the reproductive organs on the 

 receptacle, or base. Take one of the stamens 

 and carefully observe it ; it consists of two 

 parts, {\\ejilament, and the anther. The former 

 of these is found to be a capillary tube for the 

 conveyance of nutrition to the anther, a vari- 

 ously shaped body placed on the summit of 

 the stamen. The anther is the'principalt>bject 

 of regard. When submitted to microscopic 

 examination, a number of minute particles are 

 seen scattered over its surface, but it it be 

 pressed, audits interior displayed, the particles 

 become innumerable ; these are, what is 

 usually termed, the pollen or fertilizing dust 

 necessary for the impregnation of the pistil, 

 or female organ of the blossom. They exhibit 

 a most wonderful variety of structure in dif- 

 ferent flowers, and have always been objects 



