SUMMER MEETING. 



39 



Fig. 6. 



pear, and these most likely merge together more or less, till finally the proto- 

 plasm simply forms a lining for the cell. This lining was once thought to be 

 the inner cell wall. Fig. 5 shows some vacuoles in very young hairs of the Pe- 

 tunia and tomato. 



Dr. Beal : No doubt all have had more or less experience with nettles. We 

 shall now hear something in regard to their structure and mode of work from 



Miss M. L. Carpenter: The stiug 

 of a nettle has a broad base made up 

 of a number of cells, and a long needle- 

 shaped point consisting of a single cell, 

 haying at its tip an enlargement or 

 bulb. The long cell is filled with pro- 

 toplasm, which often has a streaming 

 motion, moving from the base toward 

 the tip, turning around in the bulb 

 and going back again. The narrow 

 neck of the bulb turns to one side and 

 is very brittle, so that the bulb breaks 

 off when touched, thus allowing the 

 poison protoplasm to escape. 



The sting of a nettle is shown by Fig. 6, a ; while b shows the barbed point 

 of a brittle hair from a cactus. 



Dr. Beal : Among the most beautiful and interesting things connected with 

 plant growth perhaps none are more fascinating to the student than the study 

 of protoplasm as it appears in motion while seen under the microscope. The 

 streams are so delicate that I have sometimes had students, in beginning the 

 work, view the cells for an hour, make drawings and notes, and ask for another 

 specimen of something else, without having once seen or mistrusted that the 

 protoplasm was in motion. He had not yet learned to see what was placed be- 

 fore him. We shall now have our attention called to some remarks on this 

 topic, illustrated by fine drawings, by 



L. A. Bregger : There are two kinds 

 of movements of the contents seen in 

 cells, — one in which the whole mass, 

 including the chlorophyll, moves up 

 one side of the cell, across the end and 

 down the other side, and so on, — the 

 other where the streaming movements 

 take place in bands and strings along 

 the inner surface of the cell walls. The 

 movements that we studied were in the 

 hairs from stamens of Tradescantia 

 and in the stinging hairs of the nettle, 

 magnified 355 times. The streaming 



movement can only be seen during warm weather, and when the room is at a 



temperature of from 75° to 80° F. 



The hairs from the stamens of Tradescantia consist of a series of oblong 



cells, in which the bands and strings of protoplasm are seen parallel to the 



longer sides of the cells. 



There are generally two or three currents running throughout the full length 



of the cells, and between these there are smaller moving streams. At the bot- 



Fig. 



