ANCIENT PLANTS 



a single small strand of vascular tissue lying in the 

 centre. They had certain large cells, sometimes very 

 black in the fossils, which may have been filled with 

 mucilage. 



The young roots of these plants have a very charac- 

 teristic cortex, which consists of cells loosely built to- 

 gether in a lacelike fashion, with large air spaces, so 

 that they are much like water plants in their appearance 



ex. 



Fig. 108. Transverse Section of Young 

 Root of Catamites 



w, Wood of axis ; /, spaces in the lacunar 

 cortex, whose radiating strands r are some- 

 what crushed; ex, outermost cells of cortex 

 with thickened wall. 



Fig. 109. Diagram of Cone of 

 Calami tes 



A, Main axis; br, sterile bracts; 

 sp, sporophylls with four sporangia 

 s attached to each, of which two 

 only are seen. 



(see fig. 1 08). Indeed, so unlike the old roots and the 

 stems are they, that for long they were called by another 

 name and supposed to be submerged stems, but thejr 

 connection with Calamites is now quite certain. As their 

 wcody axis develops, the secondary tissue increases and 

 pushes off the lacelike cortex, and the roots become Very 

 similar in their anatomy to the stems. Both have similar 

 zones of secondary wood, but the roots do not have those 

 primary canals which are so characteristic of the stems, 

 and thereby they can be readily distinguished from them. 

 The fructifications of the Calamites were not unlike 

 those of the living types of the family, though in some 



