STRUCTURAL" CLASSIFICATION. 25 



that are not fibrous at all, but which are chiefly used as cheap substi- 

 tutes of better packing materials. The classification is as follows: 



A. FlRRO- VASCULAR STRUCTURE. 



1. Bast fibers. 



Derived from the inner fibrous bark of dicotyledonous plants or exogens, 

 or outside growers. They are composed of bast cells, the ends of 

 which overlap each other so as to form in mass a filament. They 

 occupy the phloem portion of the fibro-vascular bundles, and their 

 utility in nature is to give strength and flexibility to the tissue. 



2. Woody fibers. 



(a) The stems and twigs of exogenous plants, simply stripped of their 



bark and used entire, or separated into withes, for weaving or 



plaiting into basketry. 

 (6) The entire or subdivided roots of exogenous plants, to be employed 



for the same purpose, or as tie material, or as very coarse thread 



for stitching or binding. 



(c) The wood of exogenous trees easily divisible into layers or splints 



for the same purposes, or more finely subdivided into threadlike 

 shavings for packing material. 



(d) The wood of certain soft species of exogenous trees, after grinding 



and converting by chemical means into wood pulp, which is sim- 

 ple cellulose, and similar woods more carefully prepared for the 

 manufacture of artificial silk. 



3. Structural fibers. 



(a) Derived from the structural system of the stalks, leaf stems, and 

 leaves, or other parts of monocotyledonous plants, or inside grow- 

 ers, occurring as isolated fibro-vascular bundles, and surrounded 

 by a pithy, spongy, corky, or often a soft, succulent, cellular 

 mass covered with a thick epidermis. They give to the plant 

 rigidity and toughness, thus enabling it to resist injury from the 

 elements, and they also serve as water vessels. 



(&) The whole stems, or roots, or leaves, or split and shredded leaves of 

 monocotyledonous plants. 



(c) The fibrous portion of the leaves or fruits of certain exogenous 

 plants when deprived of their epidermis and soft cellular tissue. 



B. Simple cellular structure. 



4. Surface fibers. 



(a) The down or hairs surrounding the seeds, or seed envelopes, of exogen- 

 ous plants, which are usually contained in a husk, pod, or capsule. 



(&) Hairlike growths, or tomentum, found on the surfaces of the stems 

 and leaves or on the leaf buds of both divisions of plants. 



(c) Fibrous material produced in the form of epidermal strips from the 

 leaves of certain endogenous species, as the palms. 



5. Pseudo-fibers, or false fibrous material. 



(a) Certain of the mosses, as the species of Sphagnum, for packing 



material. 



(b) Certain leaves and marine weeds, the dried substance of which forms 



a more delicate packing material. 



(c) Seaweeds wrought into lines or cordage. 



(d) Fungous growths, or the mycelium of certain fungi that may be 



applied to economic uses, for which some of the true fibers are 

 employed. 



The bast fibers, derived from the bark of exogenous plants, such as 

 trees, shrubs, the climbing vines, herbaceous vegetation generally, are 



