338 PRACTICAL BOTANY 



5. The vascular cylinder, consisting of 



a. Four xylem groups, each of which may consist 

 of only one tracheide, while one large element often 

 occupies a central position. 



6. The space intervening in each bundle between 

 these four groups of xylem is occupied by an ill-defined 

 group of phloem, and conjunctive parenchyma. 



The arrangement of tissues at the apex of the root of Eguisetum 

 may be studied in the same way as above described for the root 

 of Aspidium Filix-mas^ and it will be found to be similar to it in 

 all the more important points. Attention should also be paid to 

 the mode of origin of the lateral roots, which here spring 

 from the pericycle, while in Ferns they arise from cells of the 

 endodermis. 



The Sporangia 



XI. Examine with the naked eye one of the pale- 

 coloured, fertile stems, which rise above ground before 

 the green vegetative shoots in the spring : observe 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. 



