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Spores may be colorless* or colored (mostly brownish or olive). The 
typical forms of spores are illustrated in Fig. 17. As may be seen also in 
these illustrations, spores may be simple,— i. e., consisting of but a single cell, 
— (A and C), or they may be divided by partition walls {septa) into two, four, 
or more compartments {loculi), when they are termed, respectively, bi-, 
quadri or plurilocular (D, E, I, H, and J). When there are longitudinal 
as well as transverse septa, the spore becomes muriform (F, G). When 
there is a small loculus at each pole (as in B) the spore is termed polar-bilo- 
cular . 
Fig. 16. Forms of apothecia. A, patelliform ( Lecidia ); B. 
cephaloid {Cladonia ) ; C. zeorine {l^ecanora >. ; D, lirel- 
liform {Gr aphis)', E, crateriform (Aco/ium); F, angio- 
carpous ( Endocarpon ). Variously magnified. (Original.) 
A few lichens have 
spores almost large 
enough to be seen ^ith 
the naked eye: the 
majority are microscopic 
and in many cases ex- 
ceedingly minute. 
The spermagones of 
most lichens so nearly 
resembles the type as 
shown in Parmelia that 
they will be easily under- 
stood without further de- 
scription. 
The size of spores is 
commonly expressed in 
terms of the microscop- 
ical unit known as a 
micromillimeter , which 
is equivalent to one 
thousandth of a millime- 
ter, and is indicated by 
the abbreviations mic., 
mm., or by the Greek 
letter micron, /a. It is 
customary to write the 
length as the numerator 
of a fraction and the 
breadth as the denom- 
inator, and to indicate 
the minimum and maxi- 
mum of each dimension. 
Thus for the spores of 
Parmelia conspersa , 
* According to Professor Tuckerman, elongated spores are typically colorless, while 
the broader forms are typically colored. Broad spores which are without color he calls 
decolorate. 
