146 OSMUNDACEAE [ch. 



describes their position as "horizontal" {I.e. p. 355). Their structure dififers 

 but Httle from that of Leptosporangiate Ferns: the central series of cells is 

 constituted as in them, but each of the four rows of the neck consists of six 

 cells in place of the usual four (Fig. 435). 



Fig. 435. Archegonium, nearly ripe, of Osmunda 

 ciitnamomea. (After Campbell.) (X525.) This 

 figure was wrongly named Matteiucia struth- 

 iopteris ( x 250) in Vol. I, p. 288, Fig. 279. 



The Embryo 

 Campbell {I.e. p. 356) gives the best account of the embryo of the Osmun- 

 daceae, which is developed from the horizontally directed archegonium. The 

 first division of the zygote is by a basal wall parallel to its axis : but the quad- 

 rant walls are also parallel with it instead of being transverse, although their 

 position with reference to the axis of the prothallium is the same: so that 

 the embryo-quadrants and the organs derived from them are situated like 

 those of the Polypodiaceous embryo with reference to the prothallium, 

 though not to the archegonium. There is somewhat less regularity in the 

 later divisions, and in this respect Osimmda appears to be intermediate 

 between the Polypodiaceae and the Eusporangiate Ferns. Moreover, the 

 embryo retains for a longer time than in the former its original nearly 

 globular form, and the cotyledon does not break through the venter of the 

 archegonium until later than in the Leptosporangiate Ferns, showing in this 

 re.spect again a primitive character (see Campbell, I.e. Figs. 198-202). The 

 foot is very large, and penetrates deeply into the prothallus, sometimes 

 extending its superficial cells as haustoria, as in Anthoceros, or Tniesipteris. 

 Frequently more than one embryo is initiated on one prothallus, but only 

 one has been observed to come to maturity. Thus the embryo in the 

 Osmundaceae, though it resembles that of the Leptosporangiate Ferns in 

 its essential features, differs in many details from them, with a cumulative 



