LYCOPODIUM. SPOROPHORE. 179 



(Tracheides) ; note the structure of the wall, espe- 

 cially where two of these adjoin one another. 



iii. In the phloem there will be found at the 

 periphery of the vascular cylinder, and alternating 

 between the successive groups of protoxylem, masses of 

 tissue with thick cellulose walls, and small cell-cavities ; 

 these are the Protophloem groups, or first formed 

 elements of the phloem. Passing from these towards 

 the centre of the vascular cylinder, the phloem is found 

 to consist of 



a. Constituents with large cavities, and very scanty 

 cell-contents. 



~b. Elements with small cavity, and obvious cell- 

 contents. 



V. Cut radial longitudinal sections through a mature 

 stem : mount as before, examine them first with a low 

 power, and note 



1. The bases of the leaves continuous with the 

 epidermis and cortex of the stem. 



2. The Cortex showing the same differentiation into 

 successive bands (a), (&), (c), as was seen in the trans- 

 verse section, 



3. The central Vascular cylinder. 



4. Small Vascular bundles of the leaf-trace, 

 which may be seen pursuing an oblique downward course 

 from the bases of the leaves, through the cortex to the 

 periphery of the vascular cylinder ; since these bundles 

 may be followed in one radial section from the leaf to 

 the central cylinder, it follows that that part of their 

 course is approximately in a radial plane. 



We can now obtain a clear idea of the Vascular 

 System of a mature shoot of Lycopodium cfavatum : 



