At ROGENS. 



Class II. ACROGENS. 



P8KU1XKOTVLKDOSKJE, Affardh, Afh. 73. 1881).— Hi 



v, tfohl. In Mart. fl. Crypt, , 

 ■ hiii. i'. till. VMS). 



Wnii this class q great advance in structure is accomplished. T 

 plicity which i » remarkable in Thallo ed for a compli 



apparatus of many kinds. All the species have stomates orbreathi 

 on th< ir surface : in the great majority there is a distinct item ind 

 the latter of which arc always arranged with perfect symmetry; and in 

 those species which approach Thallo i rystalworts, which stand 



elose upon Lichens) the thallus has all the texture of leaves, althouj 

 separate stem is refused to them. There is, however, no trace of floi 

 properlj so called : and vet in the involucre of many Liverworts, and in 

 tin' Bpore cases of Mi in arrangement of leaves occur-, which app 



the forerunner of the flowers of more perfect plants. I bow- 



iver, i re wholly missing ; that is to Bay, nothing can be found which 



ililcs the anthers ami pistil of flowering plant.-, except in -"in.- \ 

 external circumstance : we want satisfactory evidence that any i 

 Acrogens possesses organs which require to be fertilised the one by the 

 other in order to effect the generation of seeds. Hence those reproductive 

 bodies of Acrogens which are analogous to Beeds are called Bpores Mr. 

 Griffith take-, however, a \er\ different view of tin- question, and 

 true sexes t" Acrogens. 



He thinks it probable that we have at least three modifications of 

 phenomenon of fecundation "among the higher acotyledonous plants. In 

 one the male influence is applied to the apex of a pistillum, in th 

 to a nucleus without the intervention of a pistillory apparatus. In the 

 third the male influence i- exerted on a frond itself, ami i- followed by the 

 development of the young capsule from a point in the Bubstonce of tin- 1 

 corresponding to ami Bometimes distant from the place to which the mole 

 influence has been applied. This i- founded on observations modi 



AjQthocerOS in 1836, from which it would appear that tin- place of < 



of the future capsules is pointed out by a Blight protuberance, over the ape* 

 Of which a flake of matter like the so called male matter of M 

 Salvinia is spread, sending down to some distance within the frond a 

 tube-like process, which causes the dislocation of the cellsof th< with 



which it comes into contact. Th.' future capsule is Btated in I 

 to he appreciably pre-, ristent, ami its situation i- onlj point bj a 



bulbiform condensation of the tissue of the frond. The j u 

 during its development ascends along the Bame line, and push 

 oorresponding cylindrical bod} of the tissue of the frond, tie 



authors." But, it BeemS to me, that this very complexity 1 



like variations in self-propagation, than phenomena of fecundation, which. 



among the plants in which that action certainly t 

 no such m tdifications. 



A large number of Acrogens have no true spiral ■ which .. 



fined to tho more highly developed form-, such a- Ferns, Clul . and 



Horsetails; but there is a very general tendency to the production of spiral 



1 



