614 MINNESOTA BOTANICAL STUDIES. 



the branches (PI. XXXIII. fig. 2). This rule has its exception, 

 sometimes a primary filament may give off several long 

 branches, but no branchlets. When this is the case the 

 branches develop from the upper portion of an ordinary long 

 cell following the example of most species of Stigeoclonium 

 (Plate XXXIII. fig. 1). All the cells of the stem are quite gen- 

 erally constricted at the joints, and considerably or at least 

 slightly swollen at the middle portion. In their contents, the 

 cells resemble very closely those of the Pilinia stage, the amount 

 of chloropbyllous matter in the lower ones being very meagre, 

 while in those of the branchlets it is much more abundant. The 

 chlorophores are generally not so lenticular in form as those 

 of the Pilinia stage. There is seen simply an irregular band 

 of green near the central region of the cell, containing one or 

 in some cases two pyrenoids, and occasionally one or two 

 granules. A division of the pyrenoid into two precedes the 

 formation of a new cell wall at that point. The young growing 

 cells in the upper parts of the branches and those of the 

 branchlets hence contain three or four pyrenoids. When the 

 chlorophores are distinct, they appear as elongated bands, 

 lying parallel to the sides of the filament, or are somewhat 

 disc like in form, encircling the pyrenoid. 



The short cells bearing the branches vary in number from 

 three to seven in a group (PI. XXXIII, fig. 4). One or all of 

 them may give off branches or branchlets. In general one long 

 branch exactly similar in appearance to the main stem, and 

 several short branchlets occur in a group. The mode of 

 branching is irregular. Occasionally the branches arise in 

 pairs, more generally they are alternate, and sometimes they 

 are given off irregularly from the side of the filament. 



The hair- like prolongations which are developed by the 

 Stigeoclonium cells are in all respects similar to those of the 

 Pilinia filaments with the exception that they are somewhat 

 larger and attain a greater length. According to Huber (I) 

 they would be included, together with those of Chaetophora 

 and Draparnaudia, under the term "poil" (hair or bristle). He 

 considers these bristles "to be the result of a reduction of free 

 vegetative branches — the branches which stand upright from 

 the substratum to which the plant is affixed" — and he further 

 observes that this reduction can be limited to the extremities of 

 the branches; or it may extend to the entire branch; or finally 

 it may include the entire number of upright branches, which 

 are then represented by bristles standing up from a creeping 



