261 



dium mother-cell divides by a series of walls forming: an anthcri- 

 dium which in structure is almost identical with that of the 

 PolypodiacecBJ^ As the vegetative part of the male prothallia of 

 certain Polypodiace^^ may be almost as much reduced as in 

 Pthdajna^ the resemblance between such a reduced fern prothal- 

 lium and that of Pibtlaria is too obvious to be overlooked. Add 

 to these the resemblance in the sporophyte, particularly the 

 similiarity in the sporangia and the peculiar coiled vernation of the 



¥ leaves, and 



Polypodi 



and MarsiliacecB are branches, not very widely removed, of a 



common stock. 



SALVINIACE.E.f 



The Salviniacece differ entirely in habit from the other pterid- 

 ophytes, being small floating plants which in Salvinia are des- 

 titute of roots. It is only in regard to their forming two kinds 

 of spores that they resemble the Marsilidce(2, the sporangia and 

 prothallia, as well as the habit of the sporophyte, differing much 

 niore widely from the latter than do the MarsiliacecB from the 

 true ferns. 



Our knowledge of the prothalHa of the Salviniace(B is based 

 mainly on Pringsheim's| work, but it is quite likely that his and 

 Juranyi's statement that the yowng female prothallium is com- 

 posed of primordial cells, will be found incorrect, as it seems much 

 more in accordance with our present knowledge of cell-division 

 that the process is similar to that in the MarsiliacecB. A striking 

 difference between the latter group and the Salviniacece is that 

 the Marsiliacece never produce more than one archegonium, 

 whereas the Salvtmacece invariably produce several. 



*Kny, ''Uber den Bau imJ Ent\vickeUing des Farn Antheridiums," Monatsber. 

 d. Berliner Acad., 1869. Campbell, "* The Antheridium of Ferns," Bulletin 



TORREY Club, 1886. 



fHofmeister, 1, c., pp. 32S-335. Priagsheim, "Zur Morphologie der Salvinia 

 natans," Jahrb. f. Wissensch. But., iii., p. 4S4. Juranyi, '*Uber die Entwicke- 

 lung der Sporangien u. Sporen der Salvinia natans/' Berlin, 1S73, Strasburger. 

 '* Ueber Azolla," Jena, 1873. Berggren, ''AzoUa,*' Botaniska Notiser, 1S76. Arch- 

 •'^i^gci:, I. c. (See Luerssen-Handbuch. vol. T, p. 599-) Campbell, '' Zur Entwicke- 

 ^""£?sgeschichte den Spermatozoiden,*' Ber. d. Deutschen Bot. Gesellsch, April, 1887. 



tl. 



c. 



