612 MINNESOTA BOTANICAL STUDIES. 



were quite uniform in size, being 5 to 5.5 mic. in diameter. The 

 whole fragment had a diameter of 105 mic. and was about one- 

 half as long. It seemed to be an expansion of a stem coming 

 from the main body of the crystal plate. A similar but smaller 

 fragment is figured (PI. XXXII, fig. 21.) 



The crystal plates as a rule are flat and shelving, the edge 

 on one side being rounded, and on the other somewhat straight. 

 Smaller plates or shelves are thrown out from these as 

 branches. 



It may be worth while to note the fact that a large quantity 

 of the material taken from pebble "3" consisted of filaments 

 distorted in a grotesque manner. It was thought to be due to 

 the fact that their growth had taken place after the crystal 

 plates were formed, so that a filament pressing with its termi- 

 nal cell against the resisting surface during a period of rapid 

 elongation, would have been forced back, thus inevitably 

 becoming twisted, bent and misshapen in various ways. 



Another condition of quite frequent occurrence is that of an 

 enlargement of the terminal cell or cells of the branches. As 

 shown in PL XXXII, fig. 23, these cells are much above normal 

 size. These examples are not of isolated plants. If one filament 

 is observed in this state, its neighbors will quite surely be found 

 in a like condition. No explanation is offered. It may arise 

 from a diseased state of the plant or some outward force may 

 be the cause. 



The behavior of the crystals upon being treated with hydro- 

 chloric acid shows them to be calcium carbonate. From the 

 time of the removal of the material from the spring, the crys- 

 talliferous masses gradually begin to disappear and after a per- 

 iod of three or four weeks no remains of them are to be found. 



If one could be in a position to observe personally the condi- 

 tions existent at the Bellefonte spring and to have ready access 

 to fresh material, it would make a profitable study to find out 

 whether this particular species of Stigeoclonium characterist- 

 ically encrusts lime when growing in an uncultivated state, or 

 whether it has acquired this capacity only in this particular in- 

 stance as a result of living in water in which the proportion of 

 calcareous ingredients is such that a deposit would be formed 

 upon any living plant contained in it. It should be noted here, 

 that the other algal plants inhabiting the spring, as far as can be 

 learned, are species of Chara, Oscillatoria and Lyngbya. These 

 are all known to have more or less ability to encrust lime. 



