Manchester Memoirs, Vol. li. (1907), No. 8. 9 



radial and tangential sections of Lepidophloios, without 

 being able, however, to confirm Potonie's view that the 

 parichnos strands were exposed directly. In specimens 



\p OJI. ^J>®»^ 



Fig. 4. — Leaf bases of Lepidophloios (after Potonie) 

 showing parichnos strands {par) on leaf scars and also (to the 

 left) on leaf base where overlying tissue has broken away. 

 lig. =ligular pit. 



which are particularly well preserved, and which show 

 the parichnos tissue in its entirety similar to the section 

 figured by Scott {:00), fig. 57. There is no indication of any 

 break in the epidermis, but the parichnos strands run for 

 some way very close to the surface and communicate 

 with a very delicate subepidermal tissue containing well 

 developed intercellular spaces. This tissue must have 

 been defective in the specimens examined by Potonie, for 

 in his drawing of the leaf base it is represented by a 

 large lacuna. The tissue was undoubtedly a spongy 

 parenchyma or^an aerenchyma, with either transpiratory 

 or respiratory function, or possibly both. But as far as I 

 can make out in Lepidophloios it was always covered 

 over by an epidermis, and whenever this is seen at all in 

 surface view, or even occasionally in sectional view, it 

 seems to be provided with numerous stomata, offering a 

 very efficient communication with the exterior. These 

 stomata, opening as they did on the under surface of 

 the reflexed leaf base would be well protected against 

 rapid transpiration, and at the same time provide the 

 necessary air channels through the hard periderm to the 

 interior of the stem. It would seem therefore that when 



