FREE BOOKS

Author's List




PREV.   NEXT  
|<   119   120   121   122   123   124   125   126   127   128   129   130   131   132   133   134   135   136   137   138   139   140   141   142   143  
144   145   146   147   148   149   150   151   152   153   154   155   156   157   158   159   160   161   162   163   164   165   166   167   168   >>   >|  
ng into annular. 458. Scalariform ducts of a Fern; part of a bundle, prismatic by pressure. 459. One torn into a band.] _Spiral_ ducts or vessels (Fig. 453-455) have thin walls, strengthened by a spiral fibre adherent within. This is as delicate and as strong as spider-web: when uncoiled by pulling apart, it tears up and annihilates the cell-wall. The uncoiled threads are seen by gently pulling apart many leaves, such as those of Amaryllis, or the stalk of a Strawberry leaflet. [Illustration: Fig. 460. Milk Vessels of Dandelion, with cells of the common cellular tissue. 461. Others from the same older and gorged with milky juice. All highly magnified.] _Laticiferous ducts_, _Vessels of the Latex_, or _Milk-vessels_ are peculiar branching tubes which hold _latex_ or milky juice in certain plants. It is very difficult to see them, and more so to make out their nature. They are peculiar in branching and inosculating, so as to make a net-work of tubes, running in among the cellular tissue; and they are very small, except when gorged and old (Fig. 460, 461). Sec. 2. CELL-CONTENTS. 414. The living contents of young and active cells are mainly protoplasm with water or watery sap which this has imbibed. Old and effete cells are often empty of solid matter, containing only water with whatever may be dissolved in it, or air, according to the time and circumstances. All the various products which plants in general elaborate, or which particular plants specially elaborate, out of the common food which they derive from the soil and the air, are contained in the cells, and in the cells they are produced. 415. =Sap= is a general name for the principal liquid contents,--_Crude sap_, for that which the plant takes in, _Elaborated sap_ for what it has digested or assimilated. They must be undistinguishably mixed in the cells. 416. Among the solid matters into which cells convert some of their elaborated sap two are general and most important. These are _Chlorophyll_ and _Starch_. 417. =Chlorophyll= (meaning _leaf-green_) is what gives the green color to herbage. It consists of soft grains of rather complex nature, partly wax-like, partly protoplasmic. These abound in the cells of all common leaves and the green rind of plants, wherever exposed to the light. The green color is seen through the transparent skin of the leaf and the walls of the containing cells. Chlorophyll is essential to ordinary assimilation in plant
PREV.   NEXT  
|<   119   120   121   122   123   124   125   126   127   128   129   130   131   132   133   134   135   136   137   138   139   140   141   142   143  
144   145   146   147   148   149   150   151   152   153   154   155   156   157   158   159   160   161   162   163   164   165   166   167   168   >>   >|  



Top keywords:
plants
 

Chlorophyll

 

general

 

common

 

Vessels

 
branching
 
cellular
 

tissue

 
gorged
 

peculiar


elaborate

 

partly

 
nature
 

contents

 
uncoiled
 

pulling

 
leaves
 
vessels
 

liquid

 

undistinguishably


digested

 

principal

 

bundle

 

assimilated

 

Elaborated

 

prismatic

 

products

 

circumstances

 

dissolved

 

specially


matters

 
produced
 

contained

 

derive

 

pressure

 
abound
 

protoplasmic

 
complex
 

exposed

 
essential

ordinary
 

assimilation

 
transparent
 
grains
 

Starch

 

important

 
elaborated
 

meaning

 
herbage
 

consists