22 ARRANGEMENT OF VEGETABLE TISSUES. 



at regular intervals, as if formed of porous cells laid end to end, and 

 then is called Moniliform, or Beaded (Articulated Bothrenchyma). 

 2. Punctated Tissue (Glandular Woody Tissue) ; fusiform woody tubes, 

 with depressions and markings on their walls, presenting the appear- 

 ance either of a single or double circular disc. 



III. Fibro- Vascular Tissue, composed of tubes in which the thickening mat- 

 ter is deposited in the form of spiral fibres, rings, bars, or dots. 



a. Perfect Fibro- Vascular Tissue, composed of tubes, in which there is a 



complete spiral fibre. 



1. Spiral Vessels (Tracheae, Trachenchyma), in which the spiral fibre is 



elastic, and may be unrolled. 



2. Closed Spiral vessels, or closed Trachea, in which the spiral fibre is 



brittle, or its coils so united to each other, and to the membrane, 

 that they cannot be unrolled. 



b. Imperfect Fibro- Vascular Tissue, composed of tubes marked by rings, 



lines, or dots, but without a complete fibre inside. 



1. Annular Vessels or Ducts, having fibres in the form of detached rings, 



which are occasionally united by portions of fibre. 



2. Reticulated Vessels, having fibres which cross each other, or are dis- 



posed so irregularly as to form a net-work. 



3. Scalariform Vessels, having their walls marked by isolated portions 



of fibre, in the form of ladder-like bars. 



4. Dotted Vessels, having their walls marked by isolated portions of 



fibi-e in the form of opaque dots or points. 



Any of the vessels included under the Fibro-vascular tissue, may exhibit con- 

 tractions at regular intervals, so as to become moniliform. 



CHAPTER II. 



COMPOUND ORGANS FORMED BY THE TISSUES. 



43. Some plants consist of cells only, which continue throughout 

 life to produce new cells, and to perform all the vital functions. The 

 great mass of flowering plants, however, although originally cellular, 

 produces organs composed of cells and vessels variously arranged, and 

 covered by an epidermis. These Compound Organs may be divided 

 into Nutritive, or those concerned in the nourishment of the plant; and 

 Reproductive, or those which are employed in the production of new 

 individuals. The former consist of the stem, root, and leaves ; the 

 latter, of the flower and fruit. 



SECTION I. ORGANS OF NUTRITION OR VEGETATION. 

 1. STRUCTURE, ARRANGEMENT, AND SPECIAL FUNCTIONS. 



44. Under this head will be considered the tissues of which the 

 various nutritive organs are composed, the mode in which the parts 

 are arranged, and the particular function which each of the organs 

 performs. 



