670 



of llie vascular bundle near tlie pinna-bar; it contains scattered 

 cells, slightly larger than the others and with a black content. In 

 the space caused by the destruction of the inner cortex, the pigment 

 derived from these cells, is also scattered. 



The tissue surrounding the vascular bundle has been partially 

 preserved with it. It is thin-walled without intei'celiular spaces ; its 

 elements, though often very indistinct, possess a narrow lumen; 

 they are more clearly shown in some places near the pinna- bar; 

 there the jieriplieral elements seem to l)e smaller in size than the 

 innei' ones; this tissue may be considered as phloem. It is separated 

 from the inner cortex by a continuous double layer of tangentially 

 elongated cells, tiie endodermis. 



The arrangement of the xylem-tissue of tiie vascular-bundle in 

 the petiole is characteristic. Its structure is in agreement with the 

 symmetry of the petiole and its appendices. The pinnae are placed 

 in alternating pairs, tiieir position to the petiole is similar to that 

 of a leaf to an erect bT-anch : Iheir upper side is turned towards 

 the petiole. 



A pair of pinnae is symmetrical to a plane going through tiie 

 axis of the petiole and passing between Mhe pinnae. 



The vascular bundle is .symmetrical to the same plane. The 

 structure at one end of the vascular bundle will be found at a 

 higher or lower level to be on the opposite side. This is caused by 

 the alternation of the pairs of pinnae. It is evident by comparing 

 analogous structures at one end with those at the other side, that 

 the pairs of pinnae had not quite alternated, but approached the 

 subopposite position, often also present in the fronds of existing 

 Ferns. 



In section 142 the pinna-bundles are clearly shown, passing the 

 cortex and lying halfway between the periphery and the vascular 

 bundle. They are surrounded by an endodermis. The xylem-tissne 

 is nearly round, with the narrower elements (protoxylem) lying at 

 the inner side. The outer row of trachieds seems not to be fully 

 differentiated yet. When followed in their downward course, the 

 two pinna-bundles fuse, thus forming the pinna-bar, a tangentially 

 elongated reniform brindle, with two protoxylems at its inner side. 

 This bundle is seen at different levels in section 141, 140 and 142. 

 At a somewhat lower level it becomes more flattened, approaches 

 the peliolar bundle and its endodermis fuses witii that of the petiolar 

 bundle. The xylem of the latter shows in transverse section the 

 H-form, so characteristic in this genus. From a middle l)and, the 

 apolar, which is slightly thickened in its middle part and consists 



I 



