EQUISETUM. SPOROPHORE. 221 



and are divided into joints by transverse or oblique 

 walls: they correspond in general characters to the 

 sieve-tubes of the higher plants, but the sieve-structure 

 of the terminal walls is not clear. Numerous highly 

 refractive granules are found on both sides of the 

 terminal walls. 



ft. Cambiform cells of oblong form, with cellulose 

 walls. 



VIII. From buds which have been hardened in alcohol 

 cut median longitudinal sections : treat them for a 

 short time with a strong solution of caustic potash, then 

 wash them with water, and mount in strong acetic acid. 



Examine them first with a low power, and observe 

 that the nodes and internodes are easily recognised 

 in the lower, older parts of the sections: the former 

 being the points of insertion of the leaf-sheaths, oppo- 

 site which are various complications of the arrange- 

 ment of the tissues as has already been observed; in 

 the internodes the tissues show greater regularity of 

 arrangement. Note that on passing towards the apex 

 the internodes are successively shorter, and the character 

 of the tissues of both nodes and internodes becomes 

 more uniform ; also that the leaf-sheaths become suc- 

 cessively shorter. Following the axis upwards it may 

 be seen to terminate in a sharp cone, which is the 

 pnnctum vegetationis, consisting of cells undergoing 

 division, which constitute the primary meristem. 

 Here and there it may be seen that lateral buds have 

 been cut through, they are situated at the nodes, and 

 appear to be completely surrounded by the tissues at 

 the bases of the leaves; in their form and structure 

 they resemble the punctum vegetationis of the main 



