CHAPTER XVII. 

 GROWING APEX OF ROOTS. 



PRINCIPAL MATERIALS USED. 



Roots of any Lemna ; fresh, or in alcohol. 



Roots of Barley, or other grass, grown in a pot ; fresh. 



Roots of Thuja occidentalis, or other Conifer ; fresh. 



Roots of Pteris cretica, or other Fern, grown in a pot ; fresh. 



PRINCIPAL REAGENTS USED. 

 Chloral hydrate in water (8 : 5) Eau-de-Javelle. 



IT is desirable to now become acquainted with the Growing Apex 

 of Roots (the Root-tip). We begin with Angiosperms, which 

 elongate by means of an apical meristem. 



Root of Lemna. A general impression can be obtained by 

 means of some species of Duckweed (Lemna). Into a drop of 

 water upon an object-slide we place the slender thread-like 

 pendant aquatic root of some selected species of Lemna, and 

 examine it with a low power. The root-apex is seen to be covered 

 by an extinguisher-like sheath, somewhat pointed at its forward 

 end. This is the comparatively strongly developed root-cap. A 

 good insight into the structure of the root can be obtained if 

 a fresh root is examined in a drop of solution of chloral hydrate, 

 prepared from eight parts chloral hydrate and five parts distilled 

 water. After some time the root will have become so transparent 

 that we can even study its optical section with a higher power. 

 In some cases alcohol material of Lemna, examined in chloral 

 hydrate, performs good service. The extinguisher-like root-cap is 

 only attached to the extreme end of the body of the root ; the 

 residue forms a quite free sheath, in the space between which 

 and the root itself, green algae can often be seen in the fresh 



(219) 



