MR MACVICAR on the Germination of the Filices. 267 



produced by their action upon the uniform substance of the spo- 

 rule, after the soft matter in the theca has resolved itself into 

 little concretions, conducing powerfully to the preservation or 

 the vital principle in the interior, and similar to a change observ- 

 ed to take place on the surface of Vorticella rotatoria, and other 

 aquatic animalcula, when, by some accident, they have been ex- 

 posed to the action of the air, and by which the principle of life 

 has been wrapt up for several years, is not determined. The 

 sporules of these two acotyledonous tribes seem to be small con- 

 cretions of matter produced in the reproductive organs of most 

 species, possessed of the vital principle of those species without 

 the action of sexual parts, and of the power of giving rise to forms 

 of germination peculiar to the family to which they belong; 

 which intermediate forms, in their turn, and after the action of 

 the sporule has ceased, have a similar power of evolving the ma- 

 ture forms of the species. The irregularity in size, form, and 

 surface, observable even from the same theca, seems to counte- 

 nance this idea of the simplicity of the sporule. In Polypodium 

 vulgare they are comparatively large ; they vary in surface, from 

 nearly echinated to nearly smooth, and in form from globose to 

 reniform. In Pteris crispa they are generally equilateral tri- 

 angular pyramids, more or less perfectly formed ; but they vary 

 from having plane sides and sharp angles to globose. 



Still, however, though this simplicity of structure were granted 

 to the sporule of the Filices, it does not follow that this magnifi- 

 cent family must be ranked with the Acotyledones. After leaving 

 the Dicotyledones, we do not observe the same uniformity in the 

 structure of the embryo. BROWN, our illustrious country- 

 man, has shewn *, that certain Aroideae produce seeds which 

 have an appearance and economy much more nearly resembling 

 the tuber of a root ; for instead of being distinguishable into a 



* LIN. Trans, vol. xii. 



