12 WEISS, The Parichnos in the Lepidodendracecz. 



found in the ground tissue of many recent aquatic and 

 marsh plants. This stellate tissue appears at first sight 

 to go over towards the outside into a tissue consisting of 

 large rounded cells (see Fig. 2 of Plate) ; but a careful 

 examination of this tissue leads me to think that the 

 large white areas of this tissue are not cell cavities, but 

 round intercellular spaces lying between small slightly 

 irregular, or sometimes even rectangular cells. This it is 

 difficult to make out from the tissue which is dark and 

 dense, but a detailed study of it in various sections, 

 particularly the transition to it from the stellate cells 

 makes it the more probable explanation, and brings it 

 into consonance with the structure of the underlying 



Fig. 6. — The Stellate tissue (aerenchyma) in 

 which the parichnos strands terminate in Lepido- 

 dendron Hickii (slightly diagrammatic). 



tissue of stellate cells (c.p. Text-fig. 6). I believe that all 

 this tissue to which the parichnos strand joins up is 

 aerenchymatous, and it is in close agreement with such 

 tissue as one finds, for instance, in the roots of some of 

 the mangrove plants, such as Avicennia, where we also 

 get a transition from somewhat stellate cells to a tissue 

 of smaller and more rectangular cells surrounding large 

 intercellular spaces. 



What was the external boundary of this aerenchyma, 

 I am unable to state. The preservation of the tissue is 



