Chap. UI.] THE PROCESS OP AGGREGATION. 41 



before. It appeared indeed as if the stream of protoplasm- was 

 strengthened by the action of the carbonate, but it was impossible 

 to ascertain whether this was really the case. The bag-like masses, 

 when once formed, soon begin to glide slowly round the cells, some- 

 times sending out projections which separate into little spheres; 

 other spheres appear in the fluid surrounding the bags, and these 

 travel much more quickly. That the small spheres are separate 

 is often shown by sometimes one and then another travelling in 

 advance, and sometimes they revolve round each other. I have 

 occasionally seen spheres of this kind proceeding up and down 

 the same side of a cell, instead of round it. The bag-like masses 

 after a time generally divide into two rounded or oval masses, and 

 these undergo the changes shown in Figs. 7 and 8. At other times 

 spheres appear within the bags; and these coalesce and separate in 

 an endless cycle of change. 



After leaves have been left for several hours in a solution of 

 the carbonate, and complete aggregation has been eflfected, the 

 stream of protoplasm on the walls of the cells ceases to be visible; 

 I observed this fact repeatedly, but will give only one instance. A 

 pale purple leaf was placed in a few drops of a solution of one 

 part to 292 of water, and in 2 hrs. some fine purple spheres were 

 formed in the upper cells of the pedicels, the stream of protoplasm 

 round their walls being still quite distinct; but after an additional 

 4 hrs., during which time many more spheres were formed, the 

 stream was no longer distinguishable on the most careful examina- 

 tion; and this no doubt was due to the contained granules having 

 become united with the spheres, so that nothing was left by which 

 the movement of the limpid protoplasm could be perceived. But 

 minute free spheres still travelled up and down the cells, showing 

 that there was still a current. So it was nest morning, after 22 

 hrs., by which time some new minute spheres had been formed; 

 these oscillated from side to side and changed their positions, prov- 

 ing that the current had not cease<l, though no stream of proto- 

 plasm was visible. On another occasion, however, a stream was 

 seen flowing round the cell-walls of a vigorous, dark -coloured leaf, 

 after it had been left for 24 hrs. in a rather stronger solution, 

 namely, of one part of the carbonate to 218 of water. This leaf, 

 therefore, was not much oi" at all injured by an immersion for this 

 length of time in the above solution of two grains to the ounce; 

 and, on being afterwards left for 24 hrs. in water, the aggregated 

 masses in many of the cells were redissolved, in the same manner as 

 occurs with leaves in a state of nature when they re-expand after 

 having caught insects. 



In a leaif which had been left for 22 hrs. in a solution of one 

 part of the carbonate to 292 of water, some spheres of protoplasm 

 (formed by the self-division of a bag-like mass) were gently pressed 

 beneath a covering glass, and then examined under a high power. 

 They were now distinctly divided by well-defined radiating fissures, 

 or were broken up into separate fragments with sharp e<lges, and 

 they were solid to the centre. In the larger broken spheres the 

 central part was more opaque, darker-coloured, and less brittle tlian 



