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MINUTE STRUCTURE. 



(1) Epidermoid layer. The cells are oblong in 

 surface view, and rectangular in section ; the 

 cavities are closely filled with protoplasm and 

 phseophyll grains. * 



(2) The Cortex is several cells in thickness and 

 contains wide cavities filled with phseophyll 

 grains, the cells are connected by pits — these are 

 thin places in the cell- wall. The innermost layer 

 of the cortex is the thickening layer (analogous with 

 cambium in Phanerogams). 



(3) The Midrib consists of elongated cells connected 

 together into threads which run parallel to each 

 other and to the long axis ; the transverse walls 

 are interrupted in a sieve-like manner, the threads 

 are separated laterally by the jelly, which is 

 bridged over by canals ; the long walls are in- 

 terrupted by broad pits. 



(4) The Wings. The midrib is surrounded by a 

 loose network of irregularly dispersed cells, and 

 this passes over laterally into the packing tissue of 

 the wings. This tissue is made up of irregular, 

 thread-like cells similar to those of the midrib, it 

 is poor in pheeophyll grains, but is rich in oil 

 globules. A starch reaction is nowhere found. 

 The epidermoid and cortical tissues are assimila- 

 tive, the packing tissue and midrib conductive. 



(5) The Bladders are swellings which in a young 

 state are filled with threads similar to those found 



