34 Veit Brecher Wittrock. 



When the membrane of the spore has attained a not inconsiderable increase 

 in thickness, the spore reposes some time before germinating, and conse- 

 quently belongs to the class of spores which is called hypuospores. 

 With regard to its origin it may be called an agamo spore (from « 

 pr/u., without, and /«Vtoç, marriage), as being formed neutrally without 

 any fecundation. — Formation of spores may take place in all the cells 

 of the cauloïd, in the terminal as well as in the inclosed. As a rule, it 

 begins in the youngest, i. e. the terminal, cells; afterwards proceeding 

 downwards, or, in other words, basipetally, in the principal filament as 

 well as in the branches. It is these spores which give origin, by their 

 germination, to. the course of development which has now been briefly 

 described. In this manner you will. see one neutral generation, forming 

 hypnospores, follow upon another in an uninterrupted series, without 

 any metagenesis. 



The reproduction of individuals in Pithophoraceœ may, however, 

 be effected also in another way than by the formation of spores. Besides 

 the specimens which form spores there are others, which never do so. 

 These, which are, besides, distinguished by a richer ramification, trans- 

 form part of their cells into so-called prolific cells. These cells. 

 are formed simply thus: a common vegetative cell (without suffering any 

 change as to shape) grows richer in chlorophyll-coloured protoplasm 

 and starch, and is thus made fit to form a new individual. This the 

 prolific cells do, when they have been made free ') by the destruction 

 of the mother specimen, by forming a new specimen laterally near their 

 top, in the same manner as a branch — and later a system of branches — 

 is formed by a cell in the fertile specimens. That the specimens ori- 

 ginated by prolific cells have the power of forming spores is certain, 

 as well as that specimens forming prolific cells may have been origin- 

 ated by spores. I do not know with certainty, whether specimens 

 forming prolific cells may have been originated by prolific cells them- 

 selves. But it seems to me in no wise improbable. — As to the not 

 unfrequent deviations from the scheme of the development given here, 

 see the two preceding paragraphs. 



') Often two or three prolific cells remain, however, attached to cacli other. 



