570 THE AMERICAN NATURALIST. [VOL. XXXIX. 



sions of Pringsheim and Stahl in species of Funaria, Hypnum, 

 and Amblystegium and obtained negative results in a number of 

 other forms, and presents an excellent review of the subject. 

 Lang(:oi) discovered that small pieces of the sporophyte of 

 Anthoceros la-vis when laid on damp sand produced green out- 

 growths which took on the structure of young gametophytes and 

 developed rhizoids. These aposporous gametophytes most com- 

 monly arose from subepidermal cells, but they may come from 

 any layer of the cortex down to the archesporial cylinder. It 

 seems probable that the mosses at least among the bryophytes 

 are able to reproduce themselves apogamously without difficulty, 

 when normal processes of sporogenesis are interfered with and 

 if the sporophytic tissue is in contact with moisture. 



The leptosporangiate ferns, however, furnish the most con- 

 spicuous illustrations of apospory as they do of apogamy. 

 Indeed, the two phenomena are known to occur in the same 

 form in a number of instances (e. g., AtJiyrium filix-fcemina, 

 NepJirodium filix-mas, Scolopendrium vulgare, Trichomanes ala- 

 tum, etc.). Beginning with the discovery by Druery ('86a, 

 '86b) of apospory in Athyrium filix-fcemina and its variety 

 clans sima the list has steadily grown until now apospory is 

 recorded for about ten forms. In Druery's forms the prothalli 

 developed from arrested sporangia and the spore alone is left out 

 of the life cycle. But Bower ('86) very shortly brought forward 

 in Polystichum angulare pnlcherrimum a form in which prothalli 

 are developed as simple vegetative outgrowths from the tips of 

 the leaves and the life history is thus shortened by the omission 

 of both spores and sporangia. This condition is exactly analo- 

 gous to the development of protonemata from vegetative cells of 

 the sporophytes of mosses and Anthoceros. The following year 

 Bower ('87) presented a very full account of the forms of Athy- 

 rium and Polystichum just described, and a general discussion of 

 the phenomenon of apospory. Bower ('88) then extended the 

 illustrations of apospory to two species of Trichomanes, of the 

 Hymenophyllaceae ; Farlow ('89) reported it for Pteris aquilina, 

 and Druery ('93) in Lastrea pseudo-mas cristata and ('95) for 

 Scolopendrium vulgare crispum. The exceptional amount of 

 fern variation both in nature and under cultivation has not been 



