One scientist cultured Cladophora in a suspension of Azotobacter and illuminated the culture by splitting light through a prism. He observed that bacteria accumulated mainly in the region of:
| 1. | Violet and green light | 2. | Indigo and green light |
| 3. | Orange and yellow light | 4. | Blue and red light |
| 1. | Green sulphur bacteria | 2. | Nostoc |
| 3. | Cycas | 4. | Chara |