46 



DUDLEY MEMORIAL VOLUME 



They are usually not branched but may be forked once (Fig. 1, C). There 

 is a deep sinus in front within which lies the growing point of the thallus. 

 A thick midrib is developed strongly, projecting on the lower side where 

 its ventral surface is covered with numerous deep purple-red rhizoids. The 

 margin of the thallus is more or less strongly undulate and folded, but 

 these undulations are hardly distinct enough to be called leaves. The whole 

 aspect of the plant is very much like certain species of Pallavicinia, and also 

 suggests the Japanese genus Makinoa.* A section of the thallus (Fig. 3, A) 

 shows that the midrib comprises about a dozen cells in thickness, but there 

 is no trace of the conducting strands of tissue which are a constant character 

 in Pallavicinia. In Eupallavicinia (Blyttia) there is a single very con- 

 spicuous axial strand, while in Morkia, according to Cavers, there are de- 

 veloped two strands which are however much less strongly developed than 

 in Bl)rttia. In the character of the midrib, therefore, Morkia seems to be 

 somewhat intermediate in character between Ccdycularia radiculosa and 

 Blyttia. 



The wings of the thallus are composed of a single layer of cells in the 

 marginal region, but toward the midrib the wings are composed of two or 



Fig. 4. A, vertical section of the thallus apex, in which there are dorsal and 

 ventral segments cut off from the apical cell. B, C, two consecutive sections from 

 a thallus apex, in which a single basal segment is cut off. D, E, two nearly 

 horizontal sections, showing the appearance of the apical cell, x, when seen from 

 above, x 225, h, ventral glandular hairs. 



* Miyake, K. ; Makinoa, A New Genus of Hepaticae. Bot. Mag., Vol. 13, 1899. 



