16 



Veit Brecher Wittrock. 



are far from rare, especially in the principal filament. Here it does 

 not seldom happen, especially in specimens that are but half-fertile, that 

 the formation of spores takes place even quite acropetally (pi. 2, fig. 7). 

 Rules as to the order of the formation of spores which have, as it has 

 seemed to me, no exception, are l:o That the top spore has, at least 

 in shorter branches, been developed before all the inclosed spores of 

 the branch, and 2:o That the spore which is developed by the support- 

 ing cell of the branch (if such a spore be developed, which is not al- 

 ways the case), is formed later than all the spores in the supported 

 branch. — Although the material of the other species of Pithophora which 

 I have had to examine has not in general given me opportunities to 

 make observations on the order of the spore formation, still I have 

 now and then succeeded in making an observation on this head. Thus, 

 it is distinctly seen in the specimen of P. cequalis nob. which I have 

 represented pi. 1, fig. 5, that here the formation of spores takes place, 

 upon the whole, in a basipetal direction, even if the second spore from 

 above be developed somewhat later than the third. 



As has been mentioned above, the formation of spores belongs, 

 as a rule, to the cauloid part of the thalhis. As exception spores may, 

 however, be formed also in the rhizoid part at least of P. keioensis nob. 

 (pi. 4, fig. \) — 11), P. Cleveana nob. (pi. 4, fig. 14, 18) and P. polymorplia' 

 nob. (pi. 4, fig. 19). In P. kewensis nob. I have even found rhizoids 

 with as much as three spores (pi. 4, fig. 11). The formation of spores 

 in the rhizoid takes place in exactly the same manner as in the cauloid, 

 only with the difference necessitated by the different direction of the 

 increase, so that the spore is here formed not in the upper, but in the 

 lower part of the mother cell. 



As to the time of the spore formation it is, judging from the 

 observations on this head that 1 have had access to, very different in 

 different species. In P. kewensis nob. I have seen the formation of 

 spores take place in the months of July and August. Of P. cequalis 

 nob. I have fertile specimens, also collected in July. P. Cleveana nob. 

 and P. Zelleri (v. Mart.) nob. are found with spores in October, P. 

 Roettleri (Roth) nob. in January and P. sumatrana (v. Mart.) nob. in 

 March. (At what time the formation of spores takes place in P. poly- 

 morpha nob. is quite unknown to me). However, it may be probable 

 that the formation of spores takes place during longer periods of the 

 year than those . which have been indicated above for the different 

 species. 



