EQUISETUM. SPOROPHORE. 223 



of the leaf-sheaths. These cells divide, and form the 

 young buds, which subsequently appear to be completely 

 embedded in the tissue of the leaf-sheath, and ultimately 

 burst through it. 



4. It will be useful further to trace the development 

 of the several tissues, and to note their relations to-the 

 apical cell and its segments. 



IX. Cut a series of transverse sections through a 

 bud : prepare and mount them as above directed (VIII), 

 being careful to keep them in their proper order of 

 succession, and with their upper side uppermost. 



Some of the sections will only have passed through the 

 upper parts of the leaf-sheaths, which will appear as con- 

 centric rings, with a structure similar to that already ob- 

 served (III.) : note that the leaves of successive whorls 

 alternate one with another. In the centre of these rings 

 there will be found in each of the lower sections of the 

 series a transverse section of the axis, and one of 

 the sections should include the punctum vegetationis, 

 which would thus be seen from above. In this 

 preparation observe that the apical cell appears of 

 triangular outline, while the segments are arranged 

 regularly around it : from this observation, and from 

 its appearance in the longitudinal section, it may be 

 concluded that the apical cell has the form of a three- 

 sided pyramid, and that segments are cut off from 

 three- sides. From the observation of transverse sections 

 cutting the axis below the apical cell, and a comparison 

 of these results with those drawn from a study of 

 longitudinal sections, the mode of subdivision of the 

 segments should be fully made out. 



X. Cut transverse sections of a well-developed root 



