1839] 



FARMERS' REGISTER, 



15 



ihan in trees and shrubs. It has been calculated, 

 that a large gourd contains 47,000,000,000,000 of 

 them; a number so great, that it is ditFicult lor the 

 mind to form a distinct idea of it without some- 

 thing to compare it with. Prof. Lindley illustrates 

 in this way. It all the cellules of such a gourd 

 were arranged in a line, and two hundred of them 

 stretched an inch, which is about their size, they 

 would extend about nine hundred miles. The 

 cellules of the gourd are larger than those of most 

 plants. In some plants, and in some parts of 

 plants they are only y^iy th of an inch in diame- 

 ter. Of these it would take a million to cover a 

 square inch of surface; and of course a million mil- 

 lion to form a mass measuring one cubic inch. 



The cellules of the cellular tissue present a 

 great variety of ibrms. Of these, the sphere is 

 assumed as the typical or normal form. The 

 most common, modified, or secondary forms, are, 

 the eliptic and oblate spheres, disk, and six and 

 twelve-sided prisms. The typical form is that 

 which the cellules most frequently present. The 

 next most common, is that of a twelve-sided 

 prism, produced by the moderate pressure of six 

 surrounding cells upon one. When the pressure 

 of the six surrounding cells is considerable, in 

 consequence of each cell being distended to the 

 utmost by the liquid which it contains, and at the 

 same time, confined within narrow limits, the form 

 of the prism is necessarily hexagonal. A very 

 pretty illustration of the action of these same 

 causes in producing a similar effect, is afforded by 

 blowing a number of soap-bubbles within a limit- 

 ed space; for instance, in the bottom of a tum- 

 bler; each of these bubbles will be found to be a 

 perfect hexagon. If whilst the latteral pressure 

 is considerable, the upward and downward pres- 

 sures are but slight; a compression of the sides of 

 the cellules will take place, and at the same time, 

 an extension of their ends. In this way, an elip- 

 tic sphere, or even a cylinder, may be produced. 

 This is, in fact, very frequently the case. Plants 

 enlarge much more rapidly in a vertical, than in a 

 lateral direction; and, as the consequence, it is 

 found that the cellules very fi-equenily have more 

 or less of the form last mentioned. If the pres- 

 sure is very great on two opposite sides, whilst it 

 is slight in every other direction, an oblate sphe- 

 roid, or a disk, will be produced. If the pressure 

 is great in every direction, but particularly great 

 on two opposite sides, the cellules assume the 

 form of their paralleilograms. Thus the form of 

 the cellule is determined by the circumstances 

 and situation in which it is produced. 



There is a common and very important modifi- 

 cation of cellular tissue, to which the name of dot- 

 ted ducts, or canals, has been given. These ducts 

 are formed of series of short cylindric or prismatic 

 cells, placed end to end, so as to form slender co- 

 lumns, extending the whole length of the plant, 

 in which they occur. During the early part ol 

 the life of a plant, these cylinders are entire, and, 

 consequently, each column is composed of a vast 

 number of closed cavities ; but, after a time, the 

 ends of the cylinders are torn open, and the cavi- 

 ties communicate with each other, so as to form a 

 tube. At the places where the cylinders join, ob- 

 lique dotted lines are seen externally, and hence 

 this class of organs have received the name of 



exceedingly fine and transparent character. The 

 membrane which Ibrms the cellules of the pulp of 

 a strawberry, is so transparent, that the red liquid 

 which these cellules contain, appears of almost as 

 bright a red as it would if nothing were interposed 

 between it and the eye. The same remark, will 

 apply to the cellules of a common green leaf; for 

 in no instance does the coloring matter reside in 

 the sides of the cellules, or in the membrane of 

 which they are composed, but always in the liquid 

 which they contain. This membrane, however, 

 is not always of so thin and transparent a charac- 

 ter. In the hard shell of the stones of fruit, it is 

 so thick that the very cavities of the cells are a 1 

 filled up with it. Vegetable fibre, sometimes, 

 though rarely, enters into the composition of cel- 

 lules. When it does thus enter, the cellules are 

 usually composed of one long fibre each, coiled up 

 so as to form their sides ; and not of several, cross- 

 ed or interlaced. 



Such is the cellular tissue. It enters into the 

 composition of almost every part of the vegetable 

 structure ; it constitutes exclusively the pith ; en- 

 ters largely into the structure of the leaves, sepals, 

 petals, stamens, pistils and seed ; and is altogether 

 absent only from the plates of pu^e woody matter 

 of the stem, and from what are commonly called 

 the veins of the leaves, which are in reality parts 

 of the woody system. Sea- weeds, lichens, mush- 

 rooms, mosses and ferns, are entirely composed 

 of it; and are therefore termed cellular plants. 

 This tissue is supposed, to be capable, by itself, of 

 performing all the more important functions of ve- 

 getable life ; indeed, it must be, inasmuch as the 

 class of plants just mentioned, live, grow, and 

 multiply themselves, without possessing any other- 

 When combined with the other tissues, it has 

 certain objects in particular Cot which it is des- 

 tined. One of the most important of its func- 

 tions, is to absorb moisture, and gaseous matter 

 from the earth and atmosphere ; and afier effect- 

 ing a separation of such portions as are suitable 

 to the nourishment of the plant, to give off those 

 portions which are unsuitable. If a slice of elder 

 pith, (which is, as I have already remarked, com- 

 posed entirely of cellular tissue,) be placed upon 

 the side of a watch-glass containing water, and 

 be allowed to communicate, by ever so small a 

 space, with that water, the whole mass will speedi- 

 ly become saturated; and, on the other hand, it 

 will as speedily part with its water, if exposed to 

 a dry atmosphere. Possessing, in so high a de- 

 gree as it does, the power of absorbing and giving 

 out fluids, it is well adapted to the transmission of 

 the fluids of plants, from place to place. When 

 composed of cellules of a spheroidal shape, it can 

 allow fluids to pass indifferently in whatever di- 

 rection a higher propelling force may exert itself. 

 When the cellules have any other figure, they 

 will conduct the fluids most rapidly in the direction 

 of their greatest diameter. In tl7e pith, the cel- 

 lules are of a spheroidal shape, and conduct the 

 sap to whatever part of the adjacent tissues most 

 need it ; in the medullary rays, (those lines appa- 

 rently of hard woody matter which may be no- 

 ticed in a gross section of the trunk of a free, ex- 

 tending from the bark to the centre,) on the other 

 hand, the cellules of which are thin paralleilo- 

 grams, with their principal axes directed from the 



dotted ducts. Cellular tissue is generally formed I bark to the pith, the sap is conveyed in a horizon 

 of vegetable membrane ; and membrane of an I tal direction, only. Besides, absorbing, giving off 



