140 Mr. Worsley-Benison on the 



There were numerous instances of motion of entire and adult 

 plants. In tbe adult Frotomccits, and in cell families, such 

 as Volvox (jlohdtor, where several unicellular Ahjci united to form 

 a colony, motion was effected by ciHa. In the Oscillatonm, a 

 filamentous group of Al(/(c, and the Schiwmycetcs, Ahjm contain- 

 ing Bdcteriiun, Vibrio, Sjiirilluiii, and Lept(,t/trLv, there were no 

 cilia, and yet their vibratile, oscillating, and creeping movements 

 were well known, although the causes of such movements were 

 involved in obscurity. No cilia had been discovered in the 

 brisk, active diatoms, and it was supposed that they moved 

 either by minute projections of protoplasm through spots iu 

 their shells, or that their motion depended on osmotic currents, 

 set up by interchange of matter between their cell-contents and 

 the water in which they lived. 



Movements purely mechanical and due to physical causes 

 included the bursting of spore-cases in Cryptogams, such as the 

 rupture of sporanijia in ferns, the breaking-away of the operculd 

 in mosses, and the unwinding of the elastic slaters on the spores of 

 Equisetums ; also the dehiscence of anther-cells for the escape 

 of pollen, and of the fruit of flowering-plants. All these were 

 the destruction of parts resulting from structural conditions 

 acted on by external physical phenomena. In anthers, dehis- 

 cence was produced partly by pressure of the pollen-grains on 

 the coats of the anther-lobes, causing partial absorption of the 

 latter, partly by action of the fibrous cells lining the anther. 

 The two main causes of this class of movements were varying 

 power of inhibition of moisture, and varying degree of elas- 

 ticity in the tissues. These in turn were affected by the hygros- 

 copic condition of the atmosphere, as seen in the elaters of 

 Equisetum. The degree of expansion of cells due to moisture 

 varied from one-thousandth to one-half of the cell-diameter. 

 Expansion brought about by turgidity had a smaller range, 

 being only from one-eightieth to one-fifth of the diameter of any 

 cell. Curvatm-e was caused by unequal absorption of moisture, 

 and if different degrees of elasticity ensued, the equilibrium of 

 turgidity was still more displaced. The dehiscence of seed-cap- 

 sules, whether valvular, or by pores as in the poppy, or by a 

 circular slit as m the pimpernel, or by uplifting flaps, was 

 always governed by the same physical forces, where also the 

 varying anatomical structure of the several layers bore a part. 

 As examples Mr. Worsley-Benison cited the twisting of the 

 awns of oat and of other grasses, the separation of the fruit- 

 valves of wallflower, geranium, and spurge. The balsam took 

 its name, Impatieiis noli-me-hnuicye, from the fact that when ripe 

 the capsules, if gently pressed in the middle, would suddenly 

 coil up from each end, the middle would rise into a hump, and 

 the seeds be shot out to a distance of six or seven yards. 



