394 NOTES AND MEMORANDA. 



unicellular. Spores neutral, quiescent (agamo-hypnospores), 

 generally cask-shaped, single, formed by division into two of 

 the caulo'id cells, of the chlorophyll-filled and commonly 

 widened upper parts of these cells ; in germinating, as a rule, 

 dividing into two cells, the one giving rise to the caulo'id 

 and the other to the rhizoid part of the thallus. 



The character of the single genus is of course the same as 

 the order. The author divides the genus into two sections ; 



1. Pithophorse isosporese, in which the spores are all of the 

 same principal form in each S))ecies — the enclosed (intersti- 

 tial) cylindrical or cask-shaped, the terminal with the upper 

 end conical and the top sotnewhat rounded (5 species) ; and, 



2. Pithophorse heterosporese, in which the spores are of 

 several, dissimilar forms in each species, the enclosed (inter- 

 stitial) of three forms, viz., cask-shaped, cylindrical and sub- 

 irregular, the terminal as a rule of two forms, viz., cask- 

 shaped and cylindrical, but with the upper end conical and 

 the top somewhat rounded (2 species). 



Although, then, the character of the place of origin of the 

 branches in Pithophorse, as compared to Cladophorse, being 

 set some distance from, not at, the top of the cells or joints 

 whence they emanate, may appear at first sight but trivial, 

 it yet seems to carry with it further differences of a more 

 important nature, that is to say, in the mode of spore-forma- 

 tion. The vegetative joints, as further differing from Clado- 

 phora, are also described as possessing a thin non-laminated 

 membrane, and the cells are lined by a protoplasmic stratum 

 having numerous chlorophyll- granules imbedded and enclos- 

 ing a great cylindrical " vacuole." In fertile specimens, 

 always of full size, colourless cells, that is, nearly or wholly 

 destitute of chlorophyll, are to be seen besides the green ones. 

 The formation of the spore is begun in a joint by its upper 

 part widening into the characteristic nearly always more or 

 less cask-shape, on the completion of which the chlorophyll 

 contents of the lower portion pass up thereinto, the cavity 

 becoming densely packed, whereupon a septum is formed 

 cutting the mother-cell into two daughter-cells — one, the 

 upper, being the spore, the other, the lower, being the already 

 mentioned now colourless subsporal cell. The membrane of 

 the spore now becomes considerably thickened; the contents 

 often becoming brownish. In the principal filaments and 

 sometimes in the branches of P. Zelleri (v. Mart.) Wittr., 

 the whole of the contents of the subsporal cell often do not 

 pass up but become formed into a spore below the other, 

 thus forming twin-spores. This may accidentally also occur 

 in other species. As if abnormally, again, the ordinary pro- 



