264 PRACTICAL BOTANY 



2. The cortical tissue : the cells of the peripheral 

 part of it have thick stratified and lignified walls, with 

 no intercellular spaces. Passing inwards there is seen 

 a gradual decrease in thickness of the walls, and 

 increase in size of the cells, till an abrupt limit is 

 reached at 



3. The lacunar tissue, consisting of thin-walled 

 cells, which form irregular trabeculae traversing the 

 intercellular cavity in a radial direction : the inmost 

 cells of these trabeculse have a peculiar equatorial 

 constriction. 



This lacunar tissue is more typically represented in some of the 

 larger species, e.g. S. incequalifolia, S. Willdonovii, &c. It may 

 be regarded as the equivalent of the endodermis of most other 

 vascular Cryptogams. 



4. By means of these trabeculse the single central 

 vascular bundle is suspended in the middle of the 

 large air-cavity: the bundle is of elliptical outline as 

 seen in the transverse section, and is built upon the 

 concentric type : it is composed of the following 

 tissues : 



a. The pericycle, an irregular band of com- 

 paratively large, thin-walled cells, which completely 

 surround the central tissues, and abut externally on 

 the intercellular cavity, and the trabeculse. The cells 

 of this layer, in common with all the outer tissues, 

 including the epidermis, may contain chlorophyll- 

 corpuscles. 



6. The phloem, recognized as a tissue with thin 

 cellulose walls, small cavities, and sparing protoplasmic 

 contents : though reduced in bulk at the poles of the 



