88 Dr. R. Caspary on Furcellaria fastigiata 



accurate observer will by them be enabled to say, from the exa- 

 mination of an ever so minute portion of the stem of these Algae, 

 even in the absence of fruit, root and branches, whether he has 

 before him a portion of Furcellaria fastigiata or Polyides ro- 

 tundus. 



We shall first describe the structure of the cells in Furc. fasti- 

 giata and in PoL rotundus, then point out minutely the differences 

 in the internal structure of both plants, and conclude with giving 

 the generic characters of them. 



Before commencing the description of F. fastigiata, I ask the 

 reader to look at fig. 1. PL IV., which represents a transverse 

 section of the stem of F. fastigiata, and at fig. 2, exhibiting a lon- 

 gitudinal section of it. A glimpse at these figures will show that 

 the stem is composed of four different sorts of cells, or even of 

 five, if we count the two different forms of the outermost stratum 

 of cells as two different sorts. The different sorts of cells form- 

 ing the stem of Furc. fastigiata are the following : — 



1st. The epidermal cells, forming the stratum A in fig. 1 & 2. 

 The walls of these epidermal cells are transparent, colourless, or 

 with a slight green, rarely with a brownish tinge, the inter- 

 cellular spaces filled up entirely with a transparent, colourless, 

 slimy (?) mass. Strong iodine colours all light yellow. The con- 

 tents of these cells are brown, roundish, elliptical or oval grains, 

 which are not free in the cells, but attached to the walls-, by this 

 property they are particularly distinguished from the following 

 stratum of cells B, fig. 1 & 2, which contains free, uncoloured, 

 transparent grains in great quantity. The epidermal stratum A 

 shows in the form of the cells two differences in the outer part of 

 it, a, fig. 1 & 2, and in the inner part of it, b, fig. 1 & 2. The 

 outer part a, fig. 1 & 2, of the epidermal stratum contains two 

 or three layers, rarely only one layer of polygonal small cells 

 standing perpendicular upon the axis of the stem, the walls of 

 which are almost entirely covered with brown grains. Fig. 3 

 shows these cells in a transverse section, and fig. 4 represents 

 them as seen from above, where they show themselves 4-7 -sided 

 and cornered. The relative proportion of their breadth : width : 

 length = 1 : 1 : 2 to 4. The view of these cells from above shows 

 in their contents two concentric circles, but a glimpse at fig. 3, 

 which represents them as seen from the side, explains these two 

 circles directly, as the darker outermost is formed by the profile 

 of the grains on the walls of the cell, and the innermost is the 

 space in the interior of the cell, free from brown grains, but ex- 

 hibiting a light brown colour, because the uppermost wall turned 

 to the observer is covered also with the layer of brown grains. 

 The same epidermal cells are in the sporangium not so sharply 

 cornered polygonal, but rounded on the angles. The absolute 



