612 Morphologie, Teratologie, Befruchtung, Cytologie. 



of some members of the Genus Pallavicinia. (Leland Stan- 

 ford Junior Univ. Publ. Univ. Series. p. 1 — 44. 23 Fig. 1914.) 



The authors publish an extensive summary and conclusions at 

 the end of their paper. 



The thallus in the two sections of the genus Pallavicinia differs 

 in two respects. In the section Eupallavicinia, the wings are but one 

 cell thick throughout, while in Mittenia the midrib merges gradually 

 into the wings, as is the case in Mörkia and Calycidaria. In Mittenia 

 also, there is a marked difference between the prostrate, rhizome- 

 like portion of the thallus and the upright fan-shaped green bran- 

 ches. In the latter also, the formation of adventitious branches from 

 the rhizome is more common than in the species of Eupallavicinia. 



The apical cell in the three species considered in this paper is 

 a two sided one, like that of Aneiira or Metsgeria. These species 

 differ in this respect from P. decipiens, where the apical cell is a 

 three-sided prism. Pallavicinia cylindrica (Campbell), may have a 

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

 seen in horizontal section. P. {Blyttia) Lyellii, according to Leitgeb, 

 has a two-sided apical cell. 



The hooked marginal teeth, found in Mittenia, are probably 

 comparable to the leaf-like lobes of certain species of Symphyogyna, 

 and like them bear a definite relation to the Segments of the 

 apical cell. 



The Position of the antheridia in the three species studied dif- 

 fers somewhat from the descriptions given by Schiffner. In P. 

 {Mittenia) Zollingeri they cover the whole surface of the midrib, as 

 they do in Mörkia. In the related species, P. decipiens, they are 

 Said by Farmer to form a row on each side of the midrib. In P. 

 Levieri they occur in a row on each side of the midrib, 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. 



The developraent of the antheridium is much alike in all the 

 species, and conform to the usual type found in the Jtingerman- 

 niales. 



The spermatogenesis corresponds to that found in other Hepa- 

 ticae. A delicate membrane separates the pairs of spermatocytes, 

 as in Fossomhronia and Calycularia. It is possible that a „Neben- 

 körper" like that described for Marchantia (Ikeno) and for Fossom- 

 bronia (Humphrey) may be present, but this was not certainly 

 demonstrated. Woodburn believes that such a body is not present 

 in the spermatozoid. The number of chromosomes is probably eight. 



Of the three species examined, P. Zollingeri has the smallest 

 archegonial receptacle, and P. radiculosa the largest. The archego- 

 nium of P. radiculosa shows a limited apical growth due to the ac- 

 tivity of the cover-cells. 



The embryo of Pallavicinia agrees in many ways with that ot 

 other Anacrogynae that have been studied. It is perhaps most like 

 that of Aneura in the development of a very large haustorial organ, 

 or suspensor. In this respect the species under consideration seem 

 to differ a good deal from P. decipiens, and from Mörkia. Of the 

 three species, P. Zollingeri is nearest to Mörkia in the form of the 

 capsule and the larger foot. 



The species all agree in the structure of the capsule, which has 

 a more or less conspicuous terminal beak or päd, which remains 

 intact, so that the four valves of the open sporogonium remain atta- 



