the bluish-green ones (gonimia, Nyl. j glauco-gonidia, Itzigs. ; 

 collogonidia, Tuckerm.) which are more or less distinguished 

 also by their gelatinous envelopes, are considered to agree in 

 their colouring-matter with the phycochrom of certain groups 

 of Algae. The gonimous layer, in most lichens, consists of 

 gonidia. The Peltigerei differ remarkably however by a two- 

 fold gonimous system, one series of otherwise generically re- 

 lated lichens of this Family offering gonidia, and the other 

 gonimia ; but the inferior systematic value of this difference is 

 perhaps sufficiently shewn by the fact that some of the species 

 are scarcely otherwise distinguishable. The same discrepance 

 recurs in the next following family Pannariei. And finally, in 

 the next the Collemei, in which the development of gelatine 

 reaches an extreme so marked that these plants have been 

 called Jelly-lichens, we have only gonimia. The gonimous cells 

 may make their way to the surface of the thallus, and appear 

 there, enveloped in hyphse, as powdery, often cushion-like 

 heaps, which are capable of developing into new thalli, and are 

 called soredia. 



But we are not quite at liberty to stop here. The marked 

 contrast of hypha and gonidium was open to a hypothetical 

 explanation, based on the apparent relations of these organs to 

 what seemed the same in the other Classes of Thallophytes, 

 which suggested and had its exemplification in the memorable 

 labour of Schwendener. This was met however by lichenolo- 

 gists in a manner and tone often ill enough corresponding with 

 the simply objective position of the other side ; and there was 

 room for further investigation. Ideally, from the point of view 

 of those who look at lichens as autonomous, the primordial cell 

 should be referable either to hypha or gonidiuin ; but, in fact, 

 as well emphasized by Minks (Microgonid. p. 238), it is its 

 dualism which, from the beginning of our knowledge, and 

 through all its extent, characterizes the lichen-structure, and 

 determines its history. Yet this is not all. The penetrating 

 glance of the cited vegetable anatomist has demonstrated the 



