— 82— 
sion, with the constant statement of the relationship with an alga, will 
surely mislead the student. It would be much less obscure and therefore 
more satisfactory for the purpose of the keys to state that the algal cells or 
filaments are found growing within the thallus, especially since the lichen 
is parasitic about rather than “on” the algae, and at the same time bears a 
relationship to some external substratum, 
Thallus is defined as “ a more or less definite mass of hyphae parasitic 
on algae.” This new definition of thallus is surprising and confusing, and 
the author further complicates matters by neither following his own defini- 
tion nor his view that' the lichen is a fungus in all parts of the keys. For 
instance he states that the thallus in the Collemaceae is “more or less 
distinctly gelatinous ” when it is, mainly at least, the alga on which the 
lichen grows that is gelatinous, though portions of the lichen may be 
slighdy gelatinized. The thallus of Ephebe is said to be “dwarf fruticose, 
much branched, dark,” when it is the alga on which the lichen grows that 
should be thus described. Foot notes, explaining why the conventional form 
of description was followed, would have helped at these points. There are 
other similar errors which will be found easily. However, Dr. Clements has 
done as well as others, for of a large number of authors who have recently 
written regarding the lichen thallus, careful examination scarcely shows a 
single one who is consistent with whatever view of the nature of the lichens 
he attempted to follow. When we get far enough away from erroneous 
tradition regarding lichens we may be able to be consistent. 
Under Graphidaceae, page 58, we find the statement: “Mycelium 
parasitic on yellow-green algae, forming a * * * * thallus * * * -sfr 
or thallus lacking and parasitic on lichens or on bark.” There is no indica- 
tion of any relationship with bark in those species in which algae are found 
in the thallus, and the student will be misled unless a competent teacher be 
at hand. Doubtless there is no intention of saying that the thallus is para- 
sitic instead of saprophytic on bark, yet the language quoted would imply 
that. Again on page 70, we find the following: “ Mycelium inconspicuous 
and saprophytic, or parasitic on algae,” a statement which would lead the 
student to conclude that the saprophytic condition does not exist when the 
fungus grows in relationship with the alga. 
The limitation of lichen families is a matter in which there is great 
diversity of opinion. It would seem that Dr. Clements has been influenced, 
in the recognition of a few large families, by a desire to keep the lichens 
together as much as could be consistently done, while distributing them 
among fungi to the exclusion of the class Lichenes. The Gi'aphidaceae 
