POLYTRICHUM OOPHYTE GENERATION 343 



2. The dense reddish-brown band of peripheral 

 sclerenchyma, which passes over gradually into 



3. A broad, thinner-walled band of tissue, which 

 may be termed the cortex : this finally surrounds 



4. A central mass of firm, yellow- walled tissue. 

 Examine these several tissues in detail, under a high 



power, and observe that 



1. At the extreme outer limit is a thin cuticle, 

 with small and irregular outgrowths : there is no 

 clearly defined epidermal layer. 



2. The peripheral sclerenchyma consists of cells 

 with clearly stratified red walls, which are of such 

 thickness as almost to obliterate the cell-cavity. 



3. The broad band of tissue of the cortex has 

 relatively thin, yellowish or colourless walls, and 

 protoplasmic contents with starch-granules, and 

 globules of oil (compare sections treated with iodine). 



4. The central mass of tissue (which may be com- 

 pared to a vascular bundle) is not sharply limited 

 from the cortex : it consists of 



a. A peripheral, small-celled, and thin-walled 

 portion, the walls of which do not stain blue, 

 but light yellow with Schulze's solution. 



I. A central, thick-walled part, without cell- 

 contents : the thick walls stain dark brown 

 with Schulze's solution : the elements are 

 often divided by delicate septa, which are 

 not stained by Schulze's solution. This 

 tissue may be compared to the xylem of 

 true vascular plants. 



Here and there small groups of tissues similar to the 

 above may be seen in the cortex ; these are the strands 



