180 



THE MARATTIALES 



of Ophioglossum. The young leaves arise right and left in succession on either side 

 of the stem apex, and from a very early period are strongly bent over, showing the 

 characteristic circinate vernation of the Marattiaceae. Sections made through the 

 apex of the young leaf show that it has at first a definite apical cell a good deal like 

 that which is found in the stem apex, and although no satisfactory cross-sections of 

 this apical cell were found, there seems to be no question that there is present a 

 single definite initial cell which probably has much the same form as that of the stem 

 apex. The young leaf, at this stage, has the dorsal region strongly convex and 

 composed of large parenchyma cells. The apex is bent over forward and downward. 



Fig. 164. — Series of transverse sections from a young sporophyte of Kauljussia, showing the coalescence of the two primary 

 leaf traces. /^, second leaf; Z"^, third leaf; r^, second root. X40. 

 D. Stem apex more enlarged. 

 F-H. Central region of the sections. The fusion is complete in H. The shaded area is a mucilage duct. 



The tissues of the apex and the adjacent region are composed of small, actively 

 dividing cells. The young vascular bundle can be clearly seen extending nearly to 

 the apex and continuing downward into the stem until it joins the bundle from the 

 next older leaf. 



The second root arises at about the same time that the third leaf is recognizable 

 and apparently its origin is exactly the same as it is in Dancea. Its stele joins the 

 central bundle of the stem near its junction with the third leaf trace. The young 

 leaves, Hke those in Dancea, are sparingly covered with hairs and scales, but these 

 scales do not have the peltate form found in Dancea, being usually short rows of 

 stout cells; or the hair may have its base composed of an oblong mass of cells 

 attached by a narrow stalk and having its apex drawn out into a slender filament 

 composed of two or three elongated cells. The terminal cells of these hairs usually 

 stain very strongly, indicating that they contain tannin. 



The young leaves are relatively stouter than in Dancea, but otherwise resemble 

 them closely. In the young sporophyte, up to the time of the formation of the third 

 leaf, there may be no trace of the mucilage ducts, although these may be developed 



