56 MICROSCOPY. 
substance are green granules or cells called gonidia; these bear a 
strong resemblance to certain kinds of alge. 
The same double nature of the lichens is evinced in their fructi- 
fication, even more strikingly than in the simple vegetative system. 
The complete identity of fruit (apothecia and spermagona) pro- 
duced by hyphen threads of lichens with fruit of the division 
Ascomycete of the fungi has been well known, and has even led 
to the classification of this division of fungi with the lichens (by 
Schleiden in 1842). But what astonishment was created when, in 
1867, Famentzin and Baranetzky showed that the gonidia also, in 
favorable circumstances, produced fruit identical with the zoo- 
spores of algæ. 
The question presses home more and more, whether the lichen 
is a single individual whose development follows these two diver- 
gent paths, or whether two distinct individuals out of different 
natural classes have combined together to live a united life. 
On the former supposition, the complete agreement of the goni- 
dia of lichens with certain alge, and the fact that gonidia freed 
from the lichen threads in which they lie embedded possess the 
power of independent life and development (in which state they 
cannot be distinguished from algz): these two considerations 
have led to the almost inevitable conclusion that numerous genera 
of algee (as supposed) are undeveloped or, it may be, abnormal 
states of lichens. Famentzin and Baranetzky have lately adopted 
this theory. On the other hand, De Bary (1866) has pointed out 
the possibility that in the case of the ‘‘jelly-lichens” (Gallert- 
~ flechten) the gonidia may be real alge which have assumed the 
ae mea of lichens because parasitic fungi (of the family Ascom- 
os > æ) have united themselves with them. 
_ Since 1867 Schwendener has extended this theory over the 
- ihote class of lichens. According to him lichens consist of 
n algæ spun over, and swallowed up, as it were, in the meshes of 
the mycelia of certain fungi. ‘There seemed one thing only needed 
to establish this theory, namely, to succeed in raising lichens by 
sowing the spores of fungi on gonidian-like alge. This experi- 
ment has been successfully carried through in the case of a given 
species of the genus Collema, by Dr. Beess in 1871. 
Although this would seem to close the case, yet the new view 
, accepted by the most experienced lichenologists, They 
heads of the cage nature of the lichen, saying that the 
