EQUISETUM. SPORANGIA. 225 



serve that the internodes and leaf-sheaths of the lower 

 part of it are similar to those of the vegetative axes. 

 Passing upwards, note that the last leaf-sheath below 

 the spike is of smaller size than the rest. The spike 

 itself is covered by closely-arranged peltate scales, of 

 hexagonal outline as seen from without : these are 

 arranged in more or less regular whorls. 



Remove some of the scales, and examine one of them 

 in detail: it consists of a thin pedicel by which it is 

 attached to the axis ; the pedicel widens out towards 

 its apex into a flattened shield-like structure, from the 

 lower surface of which a number of sacs (Sporangia) 

 are suspended. 



XII. Cut transverse sections through a spike, so as 

 to include some of the scales : mount in glycerine, and 

 observe under a low power. There will be seen a 

 bulky Pith, a ring of Vascular bundles, and a band 

 of cortex. The Pedicels will appear extending 

 radially from the axis, and widening at the outer limit 

 into the peltate expansion, on the lower surface of 

 which two sac-like Sporangia may be seen. 



Note that a vascular bundle runs up the pedicel, 

 and ramifies in the peltate expansion. 



Examine one of the sporangia under a high power, 

 and note 



a. The Wall which is one layer of cells in thickness : 

 the walls of these cells are strengthened by a spiral or 

 annular thickening : the wall ruptures by a longitudinal 

 slit on the side next the pedicel. 



b. Many Spores may be found in the sporangia, or 

 scattered through the glycerine : examine them care- 

 fully, and observe the spirally-coiled Elaters, and the 



Q 



