264 
POPULAR SCIENCE REVIEW. 
further illustrates the views put forth by him in a previous 
communication to the Academy of Sciences at Paris, accepting 
in its full extent Schwendener’s theory as the only one capable 
of explaining satisfactorily many obscure phenomena in the 
physiology of lichens. He accounts for its rejection by lichenists 
from the circumstance of Schwendener not having sufficiently 
demonstrated the relations of the hyphse and the gonidia, and 
the manner in which their connection is established. For, as 
he observes, it is of essential moment to show that these rela- 
tions are such as necessarily involve the idea of parasitism, and 
that apart from this they cannot otherwise be rightly inter- 
preted. Noticing the great similarity presented by the gonidia 
of lichens to certain algal types, he argues that this is not a 
merely accidental circumstance, inasmuch as these gonidia 
multiply and reproduce in the same way as the corresponding 
algse, and in entire independence of the hyphse. At consider- 
able length he passes in review an extensive series of lichens, 
and, as the result of numerous observations, identifies their 
gonidia with certain algal genera and species. 
Adopting the two groups of Schwendener already referred to, 
he examines first the Ghlorophyllacece , viz. : Trentepohlia , 
Mart. ; Phyllactidium, Kiitz. ; Protococcus , Ag. Of these 
he has traced the resemblance between Trentepohlia and 
lichen-gonidia in thirteen genera, viz. 1. Roccella , as already 
pointed out by Schwendener ; 2. Lecanora , in numerous 
species ; 3. Dirinia repanda , Fr. ; 4. Coenogonium , Linldi , 
Ehr. and (7. confervoides , Nyl. ; 5. Byssocaulon niveum , 
Mnt. ; 6. Lecidea lutea (Dcks), and L . microsperma , Nyl. ; 7. 
Graphis elegans , Ach. ; G. contexta , Pers., and G. heterospora , 
Nyl.; 8. Opegrapha varia , Pers., and 0. herb arum, Mnt.; 
9. Stigmatidium crassum , Duby. ; 10. Arthonia cinna- 
barina, Wallr. ; 11. Melaspilea arthonioides ; 12. Chiodecton 
myrticola , Fee, and 0. nigro-cinctum , Mnt. ; 13. Verrucaria 
nitida , Schrad., in which, as well as in several Graphidei , it 
had formerly been recognized by De Bary. The genus Phyllac- 
tidium he regards as furnishing the gonidia to Opegrapha 
filicina , Mnt. ; while a species of Protococcus , viz. P. viridis , 
Ag., is similar to the gonidia of Physcia parietina , as proved 
by sowing the spores of the latter upon the former. Similarly 
he reviews Schwendener’s other group, the Phycochromacece, 
and finds the following genera belonging to it furnishing 
gonidia to various genera and species of lichens : — 1. Galothrix , 
Ag., to Lichina ; 2. Scytonema , Ag., to Ephebella Hegetsch - 
weileri, Itz., to the cephalodia of Stereocaulon ramulosum , 
Sw, and to various Pannarice ; 3. Lyngbya , Ag., to Stereo- 
caulon ramulosum ; 4. Nostoc to Gollema , Arnoldia, Physma , 
