EVOLUTION- OF ANGIOSPERMS THROUGH APOSPORY 163 



tion that a much more extensive reduction has taken place in 

 the angiosperms. Apospory affords a suggestion of a method 

 by which the independent vegetative prothallus of the ancestors 

 of the angiosperms may have been directly eliminated instead 

 of being gradually reduced to a non-functional status. 



VEGETATIVE CAPSULES OF MOSSES AND FERNS. 



When once a capsule like that of Anthoceros had taken on 

 the vegetative functions of the thallus there would be nothing 

 unreasonable in expecting that it might also be able to pass a 

 resting stage in the dried condition, revive again on the recur- 

 rence of favorable weather, and send out fresh root-hairs to 

 draw moisture from the soil, just as the young fern-plant does. 

 The capsules of mosses sometimes give rise to delicate proto- 

 nema-like filaments, as though attempting to produce roots and 

 thus to maintain an existence independent of the parent leafy 

 axis. This possibility is quite within their reach, as far as 

 powers of assimilation are concerned, for the vegetative tissues 

 of moss-capsules are highly differentiated and even provided 

 with breathing-pores, which the leafy part of the plant does not 

 have. In the moss genus Buxhaiiniia the leaves are reduced to 

 mere rudiments deficient in chlorophyll, showing that the assimi- 

 latory and vegetative functions have been definitely transferred 

 to the large, hollow-walled capsule. 



The independent existence of the vegetative Anthoceros cap- 

 sule would afford a plant like a seedling angiosperm with its 

 two cotyledons, but bearing spores on the inner faces of the 

 cotyledons. No steps are required which have not been closely 

 paralleled in the evolution of one or another of the archegoniate 

 plants. 



ACROGENOUS VEGETATIVE PROPAQATION. 



The further stages of progress toward angiospermy are 

 equally supported by precedents in the vegetable world. An 

 intercalary lengthening of the periods of vegetative growth and 

 propagation marks the histories of many groups of higher plants. 

 The simplest thallose liverworts, the Ricciaceai, are annuals, 

 but the Marchantiaceae are perennial, one thallus growing out of 

 the tip of another in indefinite succession. The primitive mosses 



