94 



VASCULAR CRYPTOGAMS 



fine anastomosing branches between the lateral veins. The placenta or 

 receptacle on which each sorus is seated is a cushion-like outgrowth of 

 the vein. The sporanges are altogether destitute of an annulus ; the 

 wall always consists of several layers of cells. In Angiopteris the 

 sporanges which make up a sorus are quite distinct, ovoid, and sessile, 

 and dehisce by a vertical fissure on the inner side. In all the other 

 genera they are more or less confluent, and the entire boat-shaped sorus 

 is then known as a synange ; but each sporange still dehisces separately 

 by a vertical slit on its inner side ; or, in Dan^a, by an apical pore. 

 The coalescence is most complete in Kaulfussia, where the circular 

 sorus has the appearance of a plurilocular basin. The sorus is usually 

 surrounded by flat lobed hairs of epidermal origin, forming a kind of 



Fig. 71. — A, under side o{\&2S o{ Amiopteris caudata ; B, o{ Marattia ; i'. sori ; C, sorus of 

 Marattia cut through, showing open sporanges. (After Goebel.) 



involucre. The true indusium is sometimes altogether wanting. The 

 sporanges originate from the tissue of the leaf itself. The placenta is 

 first formed as a cushion-like outgrowth of the fertile vein, partly from 

 the epiderm, partly from the subjacent tissue. On this originate, in 

 Angiopteris, the separate sporanges as papillae, each composed of a 

 number of cells. In Marattia, however, while the two rows of sporanges 

 are distinct, those of each row are confluent from the first, but each has 

 its own archespore. The primary mother-cells of the spores are formed 

 at an early period within the archespore. 



The spores are formed in fours within their parent-cells, and resemble 

 in general character those of typical ferns. Two different forms of spore 

 sometimes occur in the same species, but they present no difference on 



