8 Livingston : Chemical stimulation of a green alga 



All of the data given are derived from cultures repeated several 

 times. The number of the cultures amount to 1,048 in all. 



Experimentation 



I. Preliminary. — The responses of the filamentous form of 

 this plant to toxic salts are of three somewhat distinct types : (1) 

 death, (2) change in phenomena of growth, and (3) change in 

 phenomena of reproduction. The fatal concentration was deter- 

 mined for most of the salts tested. At a concentration somewhat 

 below the fatal strength, all of the salts cause the filaments to 

 take the palmella form. That is, the presence of the toxic salt 

 causes the plant to behave in this regard as though it had been 

 placed in a solution of relatively high osmotic pressure. The 

 cylindrical cells become spherical and division proceeds in the 

 normal manner as described for the palmella form. But many of 

 the salts also produce, at a certain concentration, another response, 

 namely an acceleration in the production of zoospores, so that a 

 poisoned culture shows zoospores sooner and in greater number 

 than does the control without the poison. This often occurs at a 

 concentration where only the palmella form is produced, and here 

 the zoospores cannot germinate as filaments. They act in this 

 case as though they had been placed in a strong solution. Some 

 of them die and others simply enlarge and become free palmella 

 cells. These points will be discussed more fully farther on. 



II. Statement of results. — Following is a description of 

 the responses to the different reagents employed. The salts are 

 arranged in alphabetical order according to the English name 

 of the metal. The figures are all camera drawings and the mag- 

 nification is about 300 diameters. 



/. Aluminium nitrate (A1 2 (N0 3 ) 6 ). — Filaments are all killed 

 in /m 0,000. In 5/// 1 00,000 most of the cells die, but what few 

 resist the poison for the first week develop into the palmella form. 

 No zoospores are produced. (See fig. 7, wherein are shown a 

 parenchyma-like mass of Gells, three groups of two cells each, and 

 two single cells. Of one of the groups of two, one cell has died 

 after making the palmella form, as is indicated by the granules 

 within. The similar granules lying about the culture are remains 

 of dead, cells.) In a concentration of ///i 00,000 the majority of 



