993 



group would include the Asarals and their allies, and the other the 

 Umbellals, &c. 



Beyond these lie three other double groups, which, while they are 

 esseniiaUy exogenous in their structure, yet do they exhibit such mo- 

 difications and peculiarities as warrant us in viewing them in the light 

 of transition or connecting links between the Exogens proper and the 

 outermost groups of the system. These transition groups are : — 



1. DictyogenSj divisible into two groups ; one containing the Dios- 



coriacese, the other the Tiilliaceae, with their allied plants 

 respectively. This group is analogous, in position at least, to 

 that formed by the marsupials and birds combined. 



2. Gymnogens, divisible into acrogenous and exogenous, the former 

 including the Cycadaceae, the latter the Taxaceae, and collec- 

 tively analogous to the double group of reptiles. 



3. Rhizogens, divisible into mycelious and thallous, the former in- 

 cluding RaiSlesiaceae, the latter Balanophoraceae, and collectively 

 analogous to the double group of fishes. 



With these three groups, Dictyogens, Gymnogens, and Rhizogens, 

 the exogenous orders terminate ; in the same way as the Vertebrata 

 are completed by the birds, reptiles and fishes. 



Beyond the Dictyogens, and connected by them with the Exogens 

 proper, is the double group of Endogens, divisible into complete and 

 incomplete, the former including the Palmals, as exhibiting the per- 

 fection of exogenous structure, and the latter the Glumals : thus, in its 

 twofold composition being analogous to the Articulata of the animal 

 kingdom, divided into the Pterota and Aptera. 



Beyond the Gymnogens, which connect them with the Exogens 

 proper, lies the double group of Acrogens, divisible into those with 

 distinct spiral vessels, including the Filices, and those in which spiral 

 vessels are less distinct, or altogether absent, including the Musci, 

 Equiseta, &c. This group is analogous to the MoUusca among ani- 

 mals, divided into Vermes annelida and Vermes mollusca. 



Beyond the Rhizogens, by which they are connected with the Ex- 

 ogens proper, is the double group of Thallogens, divisible into the 

 mycelious and thallous, the former including the Fungals, the latter the 

 Lichenals and Algals. This group is analogous to the Radiata, 

 divided into the Radiata echinodermata and Radiata zoophyta. 

 And it is at this point that the animal and vegetable kingdoms may 

 be said to coalesce, by means of those anomalous beings with respect 

 to whose position in either kingdoms naturalists are as yet by no 

 means agreed. 



