ion 



TISSUES, VEGETABLE. 



TISSUES, VEGETABLE. 



1073 



exogenou* aud endogenous plant* there ii a constant tendency to the 

 imtritiou of the colU at either end, so that an elongated cell U thus 

 formed. These cell* arc sometimes called vessels, and constitute the 

 basii of what U called Vascular Tissue, Several cell* may join together, 

 and the intermediate part* of their walls being absorbed, they form 

 a long tube or Tesaet This is the way in which the longer and larger 

 forms of vascular tissue are probably formed. (Pig. 4, d, e.f, g. A, i.\ 

 Somrtimes thii nutrition manifests iUelf in more than two directions ; 

 we then have what are called Stellate Cells. These cells are seen 

 beautifully in the common rush, and all sorts of modifications of them 

 are seen in water-plants, where the interstices between the projecting 

 and united part* of the stellate or irregular cells are filled with air. 



Cells grow or develop in two ways. First, by taking up the 

 nutritive matters into the cell-wall, which thus becomes enlarged ; 

 second, by the deposit of new materials in the inside of the cell-wall. 

 In the cases above referred to the forms produced arc the result of 

 growth by iutus-susception, but in a large number of cases the cells 

 and vessels of the tissues become curiously ornamented by deposits in 

 their interior. The most frequent form which these deposits take is 

 that of a spiral fibre (Jig. 1, <0> which is found in the interior of the 

 cell* or vessels. This deposit may be so regular as to form a fibre, 

 which may be separated from the walls of the cell ; but more fre- 

 quently it happens that these deposits assume the form of rings, dots, 

 bars, or even pores. (Fig*. 2 and 4.) They have thus given names to 

 various kinds of tissue. 



In all these cases the interior protoplasm, endoplast, or primordial 

 utricle, seems to be the seat of nutritive activity. Our knowledge of 

 the movement of the contents of the cells of plants is no longer con- 

 fined to a few isolated cases, but has been observed in so large a 

 number of cases as to lead to the inference that it is universal. It is 

 also known that many of the currents observed assume a spiral 

 direction, and it has been inferred that the spiral deposits are the 

 result of such currents acting in the cells. The recent observations 

 of Branson and Wenham have also showu that these currents are duo 

 to the active molecular movements that occur in the primordial utricle 

 of the cell in which the movements have been observed. 



One of the most interesting forms of nutrition is the case in which 

 the active ondoplast of protein projects beyond the cell-wall, and 

 formt upon its surface a moveable hair-like projection, to which the 

 name Cilium has been given. These cilia are the causes of the active 

 locomotion observed in many of the spores of the Alga, and of such 

 compound unicellular plants as Yolrox globator. [ClUA; YOLVOCINE.E.] 



The tissues of plants formed in the manner above referred to assume 

 a variety of appearances, and vegetable physiologists have accumulated 

 a Urge number of terms to express them. The following sketch will 

 however give an idea of the general forms they assume : 



I. CEI.LUI.AK. 



Tissue composed of membrane in the form of cells whose length does 

 not greatly exceed their breadth. 

 A. Parenchyma. 



Tissue composed of cells. 



1. Incomplete. 



2. Complete. 



S. Intercellular System. 



Tissue in which cells are absent 



1. Original cavities. 



2. Cavities subsequently formed. 

 ( '. Epidermal System. 



Tissue on the surface of plants. 



1. Kpidermis. 



2. Appendicular Organs. 



a. Papilln. 

 6. Hairs, 

 r. Seta;. 

 d. Stings. 

 r. Prickles. 

 /. Wart*. 



II. FIBRO-CELLDLA.R. 

 Tissue composed of cellc, in the inside of which fibres are generated. 



a. Genuine. 



1. Fibrous cells. 



b. Spurious. 



2. Porous cells. 



3. Dotted cell*. 



III. VASCULAR. 



Tinue composed of cylindrical tube* of membrane, continuous, or 

 overlying each other at their Midi. 



1. Pleurrnrliyma, with the sides of the tubes thickened and taper- 



ing to each end. 



2. Vinenchyma, the sides of the tubes of which anastomose, and 



convey a peculiar fluid. 



IV. FIBRO-VASCULAB. 



Tisxue composed of tubes, in the inside of which one or more spiral 

 fibres are more or lea* perfectly developed. 



a. Genuine. 



1. Spiral vessels. 



2. Annular vessel*. 



3. Moniliform vessels. 



b. Spurious. 



4. Scalariform vessels. 



5. Porous vessel*. 



(Bothrtnckyma.) 



6. Dotted vessels. 



We shall now proceed to give a short description of tho principal 

 forms these tissues assume. 



Cellular Tissue ; also called Utricular and Vesicular Tissue ; the 

 Parenchyma of Lindley and Morren, and others, Tela Cellulosa of 

 Link, and Contextus and Complexus Cellulosus of older writers; 

 Zellgewebe, German ; Tissu Cellulaire, French. This tissue consist* 

 of cells or cavities, which are closed on all sides, and are formed of a 

 delicate mostly transparent membrane. It is present in the whole 

 vegetable kingdom ; and all the lower forms of plant*, constituting 

 the class Thallogau ( Lindley}, are composed entirely of it, aud have 

 hence been called CcUuIara. In the higher plants it is most abund- 

 ant in fruits and succulent leaves. It exists in larger quantity in herbs 

 than trees, and the younger the plant is the more it abounds, and 

 constitutes the entire structure of the embryo. 



The normal form of the cells is spheroidal, and when they exist in 

 this or in an elliptical form, aud only touch each other at a few point* 

 without exerting pressure, they constitute the tissue called by Meyen 

 Merenchyma. The cells in this case may form a regular or irregular 

 layer, a distinction which may be of some importance. Such tissue is 

 found in many parts of plants, especially those which are delicate and 

 easily torn, as in the pulp of fruits like the strawberry, in the petals 

 of the white lily, in the stem of Cactiu penduliu, where they are 

 spheroidal, and in the leaf of the Agate Americana, where they are 

 elliptical The cells also which constitute the entire of many of the 

 lower plant* belong to this division of cellular tissue. They are seen 

 separate or loosely adhering to each other in the Protococcui niralit, 

 the plant of the Red-Snow [Ssow, RED], in many of the smuts and 

 brands, as Uttdago and Undo. Chrooltptu, and many of the lower 

 forms of Alga and fungi, consist of filaments which are entirely com- 

 posed of spheroidal cells arranged one upon another. 



In the higher forms of plants the vegetative force is greater, and a 

 greater number of cells being generated in a given (space, they press 

 on each other on all side*, assuming a variety of forms, and constituting 

 the tissue called by Meyen Parenchyma. The principal varieties of 

 Parenchyma distinguished by Meyen are : 



1. The Cubical, which exist* in the cuticle of some leaves, aud is 

 not unfrequently met with in bark and pith, as in the pith of Viicum 

 album. (Pty. 1, c.) 



Fig. 1. 



2. The Columnar, of which there are two varieties : the Cylindrical 

 (Cylindrenchyma of Morren), examples of which may be seen in Chara 

 and in Agaricui nnucaritu } the Prismatical ( Prismenchyma ), fre- 

 quently seen in the pith and the bark of plants, and when compressed 

 it becomes the muriform tissue (Jig. 1, <), which is constantly found 

 in the medullary rays, and has it* name from the cells being arranged 

 as bricks in a wall 



8. The Dodecahedral : the natural form of parenchyma when the 

 cells are of equal size and exert on each other equal pressure, and when 

 cut present a hexagonal form. (Fig. 4, a, c.) 



4. The Stellated (Actinenchyma), in which the cells, from the irregu- 

 larity of their wall*, assume a star like form, seen in Muta. 



6. The Tabulated, seen in the epiphhcum of many plants : other 

 form*, as Conical (Couencbyma), Oval (Ovenchyma), Fusiform 



