On THE PITHOPHORACES. 45 
The spores, besides giving characters for the distinction of species 
by their form and size (see below in this parag.), are also useful for the 
same purpose by their being placed singly or in pairs. Whilst the 
spores are placed singly in most species, formed each by its special 
mother cell, it frequently happens in two species, P. Zelleri (v. Mart.) 
nob. and P. oedogonia (Mont.) nob., that the spores are found in pairs, 
formed two in succession by the same original mother cell. | 
The size of the different parts of the thallus also gives useful 
specific characters, because it is constant within no very wide limits in 
the different forms. I have found particularly the diameter of the prin-— 
cipal filament in the fertile specimens, and the size (length and thickness) 
of the inclosed,- cask-shaped spores to vary comparatively little. Ac- 
cording to the thickness of the principal filament the species range as 
follows: P. kewensis nob., the principal filament on an average 59 wu 
thick; P. oedogonia (Mont.) nob. and P. Cleveana nob. 70 aw; P. poly- 
morpha nob. 105 w; P. equalis nob. 109 w; P. Zelleri (v. Mart.) nob. 
120 a, P. sumatrana (v. Mart.) nob. 127 w, P. Roettleri (Roth) nob. 
165 w.*) From this list we find that the diameter of the principal 
filament for instance in P. Zelleri (v. Mart.) nob. is on an average twice 
and in P. Roettleri (Roth) nob. thrice as great as in P. kewensis nob., 
and so on. If we arrange the species according to the diameter of the 
inclosed cask-shaped spores, they will have an order not a little differ- 
ent. The first place is, it is true, occupied by P. kewensis nob. now 
also, with 81 jm, but the others follow in this manner: P. Cleveana nob. 
102 pw, P. polymorpha nob. 104 uw, P. swmatrana (v. Mart.) nob. 106 ua, 
P. equalis nob. 111 w, P. oedogonia (Mont.) nob. 114 uw, P. Zelleri (v. 
Mart.) nob. 144 uw, P. Roettleri Roth) nob. 152 w. From this we find, 
that P. swmatrana (v. Mart.) nob. and P. wqualis nob. have compara- 
tively narrow spores, whilst P. oedogonia (Mont.) nob. and P. kewensis 
nob. have thick ones, and so on. Arranged according to the length of 
the spores now mentioned we obtain the following series: P. polymorpha 
nob. 157 w, P. kewensis nob. 205 w, P. Cleveana nob. 216 nw, P. Roetileri 
(Roth) nob. 226 w, P. oedogonia (Mont.) nob. 230 w, P. Zelleri (v. 
Mart.) nob. 232 w, P. equalis nob. 250 w, and P. swmatrana (v. Mart.) 
nob. 375 w; from which follows, that P. polymorpha nob. has particu- 
larly short spores, while P. suwmatrana (v. Mart.) nob. has very long, 
1) The numbers given here and below in this paragraph are all average num- 
bers, gained by comparison of a great number of measurements. 
bY 
a 
