ISOETES 135 



(d) Are the roots attached to any special region of 

 the stem? If so, describe. 



(e) Study the cross-section, identifying the central 

 (vascular) cylinder, the epidermal layer, and, 

 between the two, the fleshy tissue composed of 

 several regions that are not distinguishable 

 to the naked eye. 



(/) Make a drawing (X 3), showing the outline of 

 the stem in cross-section, the tissue-regions 

 observed, and the attachment of the roots. 



3. The Roots. 



(a) Describe the general appearance of a single root. 

 Does it taper? Note that it is slightly fleshy. 

 Are the branches forked at the tip (dicho- 

 tomous), or lateral? Dichotomous branching 

 of roots is very rare. 



(b) Make a drawing (X 2) showing these features. 



4. The Leaves. 



(a) Carefully remove one of the outer leaves at its 

 point of attachment to the stem, first noting 

 carefully which is its inner (ventral) surface, 

 and which is its outer (dorsal) surface. 



(b) State whether the leaf is sessile or petiolate. 

 The end by which it is attached is the leaf- 

 base and the remainder of the leaf is called the 

 lamina or blade. Note that the blade is 

 subulate (awl-shaped). 



(c) Describe the exact length of the leaf in milli- 

 meters. Observe the slight shallow groove or 

 flattening. On which side of the leaf is it? 



(d) Hold the leaf up to the light and observe the 

 single vascular bundle, surrounded by air 

 chambers separated into compartments by 

 numerous diaphragms. 



