ON THE PlTHOPHORAOEiE. 



19 



III. ON THE GERMINATION AND INCREASE. 



Although I have not had opportunities of immediately observing 

 the germination of a Pithojphora *), still a close study of the rich material, 

 chiefly of P. kewensis nob., which I have had at my disposal, has made 

 it possible for me to account at least for the principal moments of this 

 act of development. 



The germination of the spores takes place, as a rule, in the fol- 

 lowing manner. The spore having been made free by the dissolution of 

 the two cells situated one on each side of the spore, and having reposed 

 long enough a ), it sends forth two conically-cylindrical processes, one 

 from each of the two opposite ends of the spore. The spore cell, thus 

 developed in a longitudinal direction, is then divided by a parting wall 

 into two daughter cells. This parting wall is, it is true, always trans- 

 versa], but sometimes obliquely transversa] — as for instance in P. suma- 

 trana (v. Mart.) nob. (pi. 4, fig. 1 sg) and regularly in P. kewensis nob. 

 (pi. 2, fig. 1, 5, 7 sg, and pi. 4, fig. 4, 5, 6, 9 sg), — and sometimes 

 transversal in a straight direction or, in other words, vertical against 

 the longitudinal axis of the spore cell — thus as a rule in P. Cleveana 

 nob. (pi. 4, fig. 16, 17 sg) and exceptionally in P. kewensis nob. (pi. 4, 

 fig. 7, 8 sg). This parting wall is most frequently situated just at the 

 midst of the germinated spore and thus divides it into two almost equal 

 parts (pi. 4, fig. 1, G, 9, 15); but sometimes it is placed a considerable 

 space above or below the midst of the spore (pi. 4, fig. 4, 7, 8, 16), thus 

 dividing it into two very unequal parts. The two daughter cells, formed 

 by the division into two of the spore cell, now increase in two diame- 

 trically opposite directions, and give origin one to the cauloid, and the 

 other to the rhizoid part of the thalms. The transversal wall which is 



') My sojourn in Kew was of so short duration, that i had not time enough 

 to succeed in any experiments of germination. After my return to Upsala I have 

 endeavoured to make spores which have been dry germinate (this succeeds, as is 

 known, pretty easily with some alga?), but J did not succeed. 



2 ) That the spores of Fithophoraceee are hypnospores may be concluded among 

 other tilings from the fact that their membrane increases considerably in thickness 

 during the ripening of the spores, a thing which does not lake place in spores intended 

 for immediate germination. 



