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BOTANY 



The Embryo 



The first division in the embryo of Marsilia is completed within about one 

 hour after fertilization. The divisions in the embryo and the development of 

 the organs correspond in all respects with that of the typical Ferns. The 

 cotyledon has no lamina, this being developed gradually in Marsilia, but remain- 

 ing undeveloped in Pilularia. 



Distribution and Affinities of Marsiliaceae 



Pilularia is represented in the United States by a single species, 

 P. Americana, which closely resembles the European P. globulifera. 

 It is not uncommon in various parts of California. Marsilia is rep- 

 resented within our territory by a number of species, of which 



A. 



FIG. U58. Equisetum telmateia. A, female; B, male, gametophyte (X 70). 



M. vestita is the best known. M. quadrifolia, which occurs in a 

 number of localities in the Eastern states, may have been introduced 

 from Europe. 



The gametophyte of Pilularia is less reduced than that of Mar- 

 silia, but the sporophyte of the latter is probably more like that of 

 the true Ferns. Of these, probably the Schizaeacese are the nearest 

 existing relatives of the Marsiliacese. 



CLASS II. EQUISETALES 



The second class of Pteridophytes, the Equisetales, is at present 

 represented by a single gemis, Equisetum, with twenty-four species, 

 of which fourteen occur within the United States. The habit of 



