276 Phillips on a Comparative Study of the 



ually this growth ceased and the plants remained stationary 

 for a season. Then a gradual decline began and no visible 

 trace of the organism would be left. In this way the spores 

 that had been formed lay dormant until the proper season 

 of the following year, and no experimental method seemed 

 to cause them to germinate sooner. 



In the study of the organisms, it was the general plan to 

 do as much on the living plants as possible. It was often 

 found difficult to keep the trichomes in natural surround- 

 ings, e. g., in the forms found creeping over the ground 

 often the mere mounting in water would bring about 

 extreme variation conditions. The organisms were studied 

 carefully in their normal conditions under various powers 

 of the microscope, the work being performed with Zeiss' 

 achromatic and apochromatic objectives of 2 mm. and 1.5 

 mm. focal lengths, and compensating oculars 4, 6, 8 and 18. 

 All of the drawings were made with the camera lucida and 

 these objectives. Culturing in various nutrient fluids which 

 would bring about accentuated or pathological conditions, 

 was found to be an extremely useful mode of experimenta- 

 tion. Cultures of a full nutrient solution were found to yield 

 particularly beautiful results ; also fluids which would either 

 feed or starve the chromatin were extremely useful. Grow- 

 ing in direct and in diffuse sunlight, under different colored 

 screens, and in darkness were also tried. Plants were grown 

 •in weak solutions of different salts, as palladious and plati- 

 num chlorides, to assist in bringing out the structure in the 

 cell wall, as recommended by Dr. Pennington (62). The 

 organisms were also cultivated under natural and artificial 

 conditions in a live cell and watched continually for long 

 periods of time. In this way the same cell could be observed 

 in different stages of its life-history. Intra-vitam staining 

 gave very interesting results, especially when carried out on 

 the life-slide and continuously watched. By this method 

 chromatic and nuclear elements were very nicely contrasted. 

 Filaments of Spirogyra were also placed among the trich- 



