Maryland Geological Survey 



423 



The epidermal cells are very small, the largest not exceeding 0.025 

 mm. in diameter, and the average being about half this size. They are 

 roughly rectangular in shape and have very thick Avails. Their most 

 curious feature, one not observed in any other species of this genus, is 

 the presence of minute, usually curved, spinelike outgrowths of large 

 numbers of the epidermal cells. These protuberances vary in prominence 



^ro' 



Pig. 14. — ^View of a preparation of the epidermis of Frenelopsis ramosissima. 



from blunt papillae of various heights to pointed spines 0.025 mm. 

 in length. These are not present on all of the epidermal cells, and some 

 preparations of the epidermis are apparently entirely smooth. Fig. 14 

 shows a characteristic bit of the epidermis dotted with these spines. 

 Some of the spines, probably all of them, have a central cavity opening 

 into the interior of the epidermal cell, which they surmount, as is 

 shown in one of the individual spines figured. The second and third 

 single spines figured show irregular cavities toward the apex which 



