SUMMARY 39 



SUMMARY 



i. The thallus in the two sections of the genus Pallavicinia differs in 

 two respects. In the section Eu pallavicinia, the wings are but one cell 

 thick throughout, while in Mittenia the midrib merges gradually into the 

 wings, as is the case in Morkia and Calycularia. In Mittenia also, there 

 is a marked difference between the prostrate, rhizome-like portion of the 

 thallus and the upright fan-shaped green branches. In the latter also, 

 the formation of adventitious branches from the rhizome is more common 

 than in the species of Eupallavicinia. 



2. The apical cell in the three species considered in this paper is a 

 two-sided one, like that of Aneura or Metzgeria. These species differ 

 in this respect from P. decipiens, where the apical cell is a three-sided 

 prism (Farmer [i]). Pallavicinia cylmdric a (Campbell [i]), may have 

 a two-sided apical cell, but more commonly it appears oblong when seen in 

 horizontal section. P. (Blyttia) Lyellii, according to Leitgeb [i], has 

 a two-sided apical cell. 



3. The hooked marginal teeth, found in Mittenia, are probably com- 

 parable to the leaf-like lobes of certain species of Symphyogyna, and like 

 them bear a definite relation to the segments of the apical cell. 



4. The position of the antheridia in the three species studied differs 

 somewhat from the descriptions given by Schiffner [2]. In P. {Mittenia) 

 Zollingeri they cover the whole surface of the midrib, as they do in Mor- 

 kia. In the related species, P. decipiens, they are said by Farmer [1] to 

 form a row on each side of the midrib. In P. Levieri they occur in a row 

 on each side of the midrib, and not on its upper side. In P. radiculosa 

 the presence of sterile areas between the groups of antheridia seems to 

 have been overlooked by previous students of this species. 



5. The development of the antheridium is much alike in all the 

 species, and conforms to the usual type found in the Jungermanniales. 



6. The spermatogenesis corresponds to that found in other Hepaticae. 

 A delicate membrane separates the pairs of spermatocytes, as in Fos- 

 sombronia and Calycularia. It is possible that a "Nebenkorper," like that 

 described for Marchantia (Ikeno [1]) and for Fossombronia (Humphrey 

 f 1 ] ) may be present, but this was not certainly demonstrated. Woodburn 

 [1] believes that such a body is not present in the spermatozoid. The 

 number of chromosomes is probably eight. 



