EQUISETUM 143 



the vegetative shoots. Study the plant in the field and dig up the 

 underground rootstocks (rhizomes). Note their extent and the 

 manner in which the plant establishes itself in the soil, its lux- 

 uriance in waste ground, and its endurance of drought. It is in 

 structure an excellent illustration of a xerophyte (see Principles, 

 p. 459), showing very striking adaptations to its life habits. 

 A. General morphology. Study entire plants, including the 

 rootstocks. Well-mounted herbarium sheets of plants col- 

 lected when the spores are shed, and another set collected 

 about a month later are excellent for comparative study. 

 In plants collected in April with spore-bearing or fertile 

 shoots note : 



1. The upright, pale yellowish, unbranched shoots bear- 

 - ing cones at the tip composed of six-sided scales. These 



shoots are the spore-hearing, or fertile shoots. Examine 

 theb: jointed structure, and in preserved material pull the 

 joints apart. 



2. Note the toothed sheaths at the joints (nodes). Each 

 tooth represents a leaf. 



3. Observe the developing, branched, vegetative shoots. Have 

 they the same jointed structure with toothed sheaths as 

 the spore-bearing shoots ? 



4. Trace the spore-bearing shoots and also the develop- 

 ing vegetative shoots to the creeping rootstock (rhizome). 

 What is the structure of the rootstock ? Has it joints ? 

 sheaths ? Where do the roots arise ? Note the tuberous 

 bodies, if present. 



Illustrate the above features in a habit sketch, with such 

 details of the joints and sheaths as are necessary to 

 make clear the fundamental morphology. 

 In plants collected somewhat later, with well-developed vege- 

 tative shoots, note : 



5. That the spore-bearing shoots have died. 



6. That the vegetative shoots have developed into tall green, 

 much-branched stalks. How do they feel to the touch ? 



