22 Weiss, The Parichnos in the Lepidodendracece. 



EXPLANATION OF PLATE. 



Fig. i . Transverse section (magnified) across the leaf cushion of 

 a Leftidodendron, allied to Lep. Hickii., showing the bifurca- 

 tion of the parichnos strand (par.). The right hand branch 

 opens into a pit-like depression, partly filled with aerenchyma, 

 which has become slightly displaced. (R 275.) 



Fig. 2. Enlarged view of portion of Fig. 1, showing the 

 aerenchyma, at the base of which is a cluster of small 

 stellate cells (st.c). Compare this figure with Text fig. 1. 



Fig. 3. Part of a tangential section of stem which has cut across 

 four leaf cushions. No. I. is cut nearest the stem, then 

 II. j III., and IV. in series. In I. the two lateral pits are 

 seen to run deep into the leaf cushion, and at this point are 

 not connected with the parichnos strands. In II. the 

 parichnos strands come closer to the pits, and these are seen 

 opening out on either side of the median ridge of the leaf 

 cushion. In III. the lateral pits are more widely open. 

 IV. is cut close below the leaf scar, and the pits are now no 

 longer seen, but aerenchyma lies below the epidermis and 

 adjoins the tissue of the parichnos. (Enlarged 4 times.) 

 (R 269 in the Manchester Museum collection.) 



Fig. 4. A transverse section across the vascular bundle (v.b.) of 

 a Stigmarian rootlet on its way out through the hard outer 

 cortex (o.c). It is accompanied on its lower side, which 

 lies towards the apex of the Stigmarian axis, by a group of 

 parenchymatous cells, in continuity with the middle cortex, 

 and consequently homologous with the parichnos of the 

 leaves. (Q 148.) 



