8o BOTANY FOR BEGINNERS CHAP. 



mud would do in a swiftly moving river. When the granules in 

 their movements go round and round the interior of the cell, 

 the movement is called rotation. 



In an old cell where the protoplasm does not completely fill 

 the interior of the cell the spaces are termed vacuoles. 

 Vacuoles are filled with cell-sap. The connection between the 

 protoplasm in different parts of the cell is kept up by strands 

 of protoplasm. In such a cell the granules move up one 

 strand and down another, much as the blood corpuscles move 

 in the blood stream. This latter movement, which is more 

 complex than that of rotation is called circulation. The indi- 

 vidual granules in the current can be seen to move with 

 unequal rapidity, according to their sizes, the smallest moving 

 fastest. 



The currents in the protoplasm are apparently irregular, now 

 advancing, now retreating, sometimes suddenly arrested, and 

 commencing again with increased rapidity. The movements 

 depend upon temperature. In winter, during frost, and in 

 summer, during dry weather, they are arrested. In spring, 

 when there is plenty of moisture and a fair amount of heat, they 

 are seen at their best. 



EXPT. 76. Obtain a plant of the American Water 'Weed (Elodea] 

 and mount a single leaf in water. Place a cover-glass on, and examine 

 wMi a high power. Note 



(i) The cells and the granules in the protoplasm. 



(ii) The movement of the granules ; they move round and round 

 this is rotation. 



(Hi) Gently"warm the slide over hot water. Examine again. The 

 temperature being raised the granules move faster. 



(iv) Now hold the slide either over a gas flame or a spirit lamp until 

 the water boils. Examine again. There is no movement, the protoplasm 

 has been killed. 



EXPT. 77. Remove a portion of the epidermis of a Stinging Nettle 

 and mount it in water ; examine with the low power. Notice 



(i) The hairs ; focus one in the centre of the field and, using the high 

 power, observe 



(ii) The cell is wider at the base than at the apex of the hair; 

 examine the protoplasm, nucleus, vacuoles, and cell-wall. 



(iii) The granules are seen in a state of motion ; they move up one of 

 the strands and down another this is circulation. 



EXPT. 78. Remove a small portion from near the core of an American 

 Apple. Mount in water and examine under a low power ; fogus a cell 



