RELATIONS OF C ALAMODENDRON TO CALAMITES. 271 



Fig. 2. Diagram of a young decorticated Calamite. a, medullary canal ; h, 

 thin layer of medullary parenchyma ; c, circle of vascular wedges, 

 each commencing internally at the internodal canal, d ; e', longi- 

 tudinal extensions of these wedges through each internode ; /, a 

 node ; g, g', primary medullary rays ; h, external orifices of the 

 vertically elongated variety of infranodal canals ; i cellular, and 

 probably also vascular, extensions, apparently connected with a 

 verticil of leaves. 



Plate XV. 



Fig. 3. Diagram of an older stem of a Calamite. a, medullary canal ; b, b', 

 exterior of the medullary cellular layer ; c', radial section through 

 a vascular wedge ; c, exterior surface of the vascular zone ; /, the 

 node ; g, primary medullary rays ; h", an infranodal canal extend- 

 ing from the exterior of the medulla {b) to the inner surface of 

 the bark, Jc; i, i', verticil of radial organs identical with i of fig. 2. 



Fig. 4. A diagram of a cube cut out of a stem like fig. 2. c, portion of a 

 vascular wedge ; g, g, portions of two primary medullary rays ; 

 I, secondary medullary rays. 



Plate XVI. 



Fig. 5. Similar cube to fig. 4, from a rare form of Calamite, in which the 

 primary medullary rays, g g, consist of prosenchyma instead of 

 parenchyma, c, vascular wedge. /, secondary medullary rays. 



Fig. 6. Similar cube, from a stem of a Calamodendron. c, vascular wedge ; 

 g, g', tissues occupying the positions of the primary medullary 

 rays, g", g", vertical layers of parenchyma separating some of the 

 prosenchymatous layers which represent the primary medullary 

 rays of Calamites. 



Botanical Laboratory, 

 Owens College, 

 Oct. ist, 1886. 



