XI THE HOMOSPOROUS LEPTOSPORANGIATyE 359 



is not formed, but as to this and the much more important 

 point, the number and character of the canal cells, Rauwenhoff 

 says nothing definite. The neck is long and straight, like that 

 of Osinunda and the Hymcnophyllacea:. 



The Embryo 



To judge from the few rather vague statements made by 

 Rauwenhoff in regard to the embryo, this more nearly resembles 

 the typical leptosporangiate type than it does Osnninda. The 

 primary root has a large and definite three-sided aj^ical cell, 

 and the divisions in the segments are very regular. 



Poirault ^ has recently made a study of the stem of various 

 species of GleicJienia, which differs a good deal from that of 

 Osinunda, and approaches that of the Hymenophyllaceae and 

 Schizaeacese. A single axial bundle traverses the stem, and is 

 separated from the sclerenchymatous cortex by a distinct 

 endodermis. Within the latter is a pericycle of several layers 

 of cells, within which is a continuous zone of phloem containing 

 large and small sieve-tubes, and phloem parenchyma. Within 

 the phloem are also secreting cells. The whole central part of 

 the stem is occupied by bundles of large scalariform tracheids 

 separated by parenchyma (Fig. 185, D). The single bundle 

 traversing the petiole is much like that of Osmunda, and the 

 lamina of the leaf does not show any peculiarities. 



The development of the sporangium is still unknown, but 

 it probably does not differ essentially from that of the 

 HymenophyllacejE, wath which it closely agrees in its mature 

 condition. In G. dicJiotoma (Fig. 185) the sporangia form 

 rounded naked sori above the terminal branch of a lateral vein. 

 They are pear-shaped, with a very short stalk, and upon 

 the outer surface is a nearly complete very distinct annulus 

 composed of a single row of large thick-walled cells. This is 

 interrupted at the top of the sporangium by three or four 

 narrow thin -walled cells, and starting from this point and 

 extending along the median line of the ventral surface are two 

 rows of narrow cells, between which the sporangium opens. 



^ Poirault (i), p. 170. 



