1 62 THE AMERICAN NATURALIST. [Vol. XXXVII. 



(I make this statement with some reserve) all cases of apogamy 

 yet observed have been in cultivated ferns. At any rate, much 

 the larger number of observ ed cases have been under artificial 

 conditions, either intentional or otherwise. This suggests at once 

 that apogamy is a pathological phenomenon. In most cases it is 

 induced by preventing fertilization, which would otherwise take 

 place, except in a very small number of instances. Exposure 

 to strong sunlight has also been found to be a factor in inducing 

 apogamy. It is also noteworthy that most cases of apogamy 

 occur in varieties which differ from the normal in being crested, 

 or that show other indications of exuberant vegetative growth 

 which may certainly imply some connection between this redun- 

 dant growth and apogamy in the gametophyte. 



Finally, as Professor Bower has pointed out, all cases of 

 apogamy recorded occur in leptosporangiate ferns, admittedly 

 the most recent and most specialized members of the class. No 

 Bryophytes nor eusporangiate ferns have yet been found which 

 exhibit apogamy. If we are to consider apogamy as in any 

 sense a reversion to a primitive condition, it is hard to see why 

 it should be confined to these highly specialized modern types, 

 and be entirely absent from the presumably much older and 

 more primitive ones. 



Mr. Lang 1 has given a very clear account of what he thinks 

 may have been the course of development of the sporophyte, 

 according to the homologous theory. He assumes that the 

 primitive form of the gametophyte was a flattened thallus, pre- 

 sumably much like the existing liverworts, although he does not 

 make this comparison. He supposes that this thallus under 

 stress of circumstances, owing to an insufficient water-supply, 

 may have given rise to spores, the spore-stage following the sex- 

 ual stage, but being an integral part of the gametophyte, and 

 not produced from the egg. It is assumed that in connection 

 with this special spore-producing function, the leafy sporophyte 



produced structure should be identical with those developed by 



