EQUISETUM SPOROPHYTE 339 



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. 



I. 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 

 smooth inner coats of the spore, which inclose a 

 protoplasmic body with a well-marked nucleus. 



Scatter fresh spores upon a slide, and breathe upon 

 them gently : then observe them under the microscope : 

 the elaters will be seen to execute active movements, 

 thus showing that they are highly sensitive to changes 

 of moisture in the air. 



By cutting transverse sections of spikes of various stages of 

 development, which have been hardened in alcohol, or in picric 

 acid and then in alcohol, mounting them in glycerine, and com- 

 paring them, the history of the development of the sporangium 

 may be traced. The chief points to be observed will be (1) that 

 the sporangia appear as multicellular protuberances ; (2) that a 



z 2 



