Ii8 " SCOURING-RUSH," OR "HORSETAIL." 



Good material of root-stocks and both kinds of aerial 

 shoots should be collected and preserved, some by 

 pressing and drying, and some, especially spore-bearing 

 shoots, in alcohol or formalin. Fresh material, if obtain- 

 able, should be used. 



LABORATORY WORK. 

 GROSS STRUCTURE. 



I. THE SPORE-BEARING SHOOT. Observe: 



1. The straight jointed stem. 



2. The circle of leaves at each joint (node). 



3. The structure of the node as seen when a stem is broken 

 at that point. 



4. The terminal cone, composed of small spore-bearing 

 leaves (sporophylls) arranged in regular order. 



5. Draw. 



II. The GREEN SHOOTS. Observe: 



1. Mode of branching. 



2. Similarity in structure of the main axis and its branches 

 to that of the stem which bears the cone. 



3. Draw two or three internodes. 



III. RHIZOME. 



Observe how the leaves and roots arise from it. Show this 

 by a sketch. 



MINUTE STRUCTURE. 

 I. THE AERIAL STEM. 



Make a cross-section between the nodes of a spore-bearing 

 shoot and of a green shoot; mount under one cover and com- 

 pare as to: 



1. The general outline of the cross-section. 



2. The ridges and furrows along the outer surface. 



