55b THE AMERICAN NATURALIST. [Vol. XXXIX. 



genesis in the Saprolegniales. Trow (:04) believes that some 

 of these forms are sexual but there can be little doubt that the 

 group as a whole is generally apogamous. There is probably 

 much apogamy in the Ascomycetes and an almost entire suppres- 

 sion of sexual organs in the Basidiomycetes but no clear instance 

 of parthenogenesis {i. e., a development from a cell whose mor- 

 phology is unquestionably that of an egg) is knownin either of 

 these groups. 



Parthenogenesis is not known in the bryophytes and pterido- 

 phytes excepting for Marsilia (Shaw, '97; Nathansohn, :oo). 

 Although there is much apogamy^ in the pteridophytes, especially 

 in the leptosporangiate Filicale^~^e new generation generally 

 develops as a bud-like outgrowth on the prothallus (vegetative 

 apogamy). There have been no nuclear studies on the parthen- 

 ogenetic Marsilia but an interesting preliminary account has 

 appeared announcing nuclear fusions in the apogamous develop- 

 ment of Nephrodium (Farmer, Moore, and Digby, 103). 



Parthenogenesis is now known in the spermatophytes for 

 Antennaria alpina (Juel, '98, : 00), several species of Alchemilla 

 (Murbeck, :oia, :oib, : 02 ; Stirasburger, :04c), Thalictrum pui'- 

 pU7-ascens (Overton, : 02, : 04), Gnetum (Lotsy, : 03), a number 

 of forms of Taraxacum (Raunkiaer, 103; Murbeck, :o4), sev- 

 eral species of Hieracium (Ostenfeld, : 04a, : 04b ; Murbeck, : 04), 



Wikstrcemia indica (Winkler, :0S), and is suspected for Ficus 

 Treub, : 02) and Bryonia dioica (Bitter, 104). A number of 

 cases of polyembryony were formerly considered examples of 

 apogamy but are now known to be developments from the nucel- 

 lus and consequently vegetative buds of sporophytic origin and 

 entirely independent of gametophytic activities. The best known 

 of these forms are Funkia, Coelebogyne, Citrus, Opuntia, and 

 Alchemilla pastoralis. Vegetative apogamy is illustrated in the 

 development of embryos from antipodal cells as in Allium odorum 



(Tretjakow, '95 ; Hegelmaier, '97) or from the cells of the endo- 

 sperm as in Belanophora (Treub, '98 ; Lotsy, '99). Synergids 

 have been reported to form embryos in a number of forms but 

 many of these have proved to be cases in which the synergid is 

 fertilized by a sperm nucleus and not examples of apogamy. 

 However, synergids are known to develop embryos apogamously 



