On THE PlTHOPHORACEiE. 



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 fi 

 thick; P. oedogonia (Mont.) nob. and P. Cleveana nob. 70 P. poly- 

 morpha nob. 105 P. cequalis nob. 109 (i; P. Zelleri (v. Mart.) nob. 

 120 P. sumatrana (v. Mart.) nob. 127 u 1 P. Roettleri (Roth) nob. 

 165 jit. *) 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 ,<(, but the others follow in this manner: P. Cleveana n ob. 

 102 ,u, P. polymorpha nob. 104 ^, P. sumatrana (v. Mart.) nob. 106 /?, 

 P. cequalis nob. Ill P. oedogonia (Mont.) nob. 114 jit, P. Zelleri (v. 

 Mart.) nob. 144 /t , P. Roettleri (Roth) nob. 152 From this we find, 

 that P. sumatrana (v. Mart.) nob. and P. cequalis 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 jit, P. kewensis nob. 205 ju, P. Cleveana nob. 216 jit, P. Roettleri 

 (Roth) nob. 226 /t , P. oedogonia (Mont.) nob. 230 jit, P. Zelleri (v. 

 Mart.) nob. 232 ^, P. cequalis nob. 250 jit, and P. sumatrana (v. Mart.) 

 nob. 375 jit; from which follows, that P. polymorpha nob. has particu- 

 larly short spores, while P. sumatrana (v. Mart.) nob. has very long, 



l ) The numbers given here and below in this paragraph are all average num- 

 bers, gained by comparison of a great number of measurements. 



