SELAGINELLA. SPOROPHORE. 167 



To confirm this, cut transverse sections of the stem about one 

 inch from the apex, and treat as above. It will be seen that the 

 elements near the poles of the xylem are already fully formed, 

 and their walls lignified, while those at the centre are still thin- 

 walled, and have protoplasmic contents. The lacunar tissue will 

 be found to be better defined in these sections. 



IV. Cut longitudinal sections of a stem of S. Martensii. 



N.B. Since, owing to its being fixed in its place only 

 by the weak trabeculse, the vascular bundle is apt to be 

 detached in cutting accurately longitudinal sections, it 

 will be found better to cut the sections slightly 

 oblique ; it must then be remembered in examining 

 them under the microscope that the sections are not 

 truly longitudinal. 



Mount some in glycerine, others in Schulze's solution, 

 and examine them under a high power, noting the same 

 succession of tissues on starting from the outside, as 

 were seen in the transverse sections : thus 



1. Epidermis \ these are hardly to be distin- 



2. Outer cortex J guished one from another ; the 

 cells of both are prosenchymatous, and thick walled, and 

 show a gradual transition to 



3. The Inner cortex with thinner walls, and of 

 parenchymatous shape. 



4. The Lacunar tissue, in which may be distin- 

 guished 



a. The outer parenchyma, consisting of short and 

 small cells. 



b. The inner cells, which are elongated in a radial 

 direction, and show the peculiar median constriction, 

 above noted in the transverse sections. 



5. The Phloem-sheath, consisting of elongated 



