1882.] of protoplasm in the motile organs of leaves. 267 



developed brain, yet it is quite apparent that in plant life we 

 do have here and there glimpses of that quick response to stimuli, 

 that wonderful irritability and spontaneity which so emphatically 

 distinguishes animal life. I should like to bring forward one or 

 two examples. Who in watching the movements of a swarmspore 

 does not notice how quickly it progresses, and yet how it avoids 

 every obstacle ? Fertilisation again shews us the same thing. Why 

 is it that the antherozoid will always go straight to the oosphere, or 

 that two conjugating cells of Spirogyra — two different individuals 

 as they are — will each protrude out their cell walls, contract their 

 protoplasm, pass over and fuse ? Is it as in the yeast that the 

 protoplasm — vibrating with that activity which we call life, com- 

 municates its vibrations to the medium and allows its fellow proto- 

 plasm to respond ; or in the case of the swarmspore does it avoid 

 those objects which do not answer to the same note as its own, or 

 seize on the food particle with whose cry it has been acquainted 

 from its youth up ? We cannot tell, for here our knowledge fails. 



Sometime ago I noticed an interesting phenomenon in the 

 swarmspores of Saprolegnia. As is well known, these asexual cells 

 are produced by the segmentation of the protoplasm of one of the 

 swollen hyphal branches. When matured the wall of the spo- 

 rangium gives way, the swarmspores escape, and after swimming 

 about actively for some minutes become quiescent and develope a 

 cell wall. But it may happen that the aperture in the sporangium 

 wall becomes shut again before all the swarmspores have passed 

 out. In that case, whereas the freed spores will come to rest very 

 quickly, those still in the sporangium will continue swimming 

 round and round their prison for some comparatively long time, 

 and will at length in their turn come to rest. 



Of the many phenomena however which connect animal and 

 plant life none are so striking to every mind as those connected 

 with movement, and it is of movement that I have to speak — 

 the movement of leaves. It was Sachs and Pfeffer in Germany 

 and Charles Darwin in England who more especially drew atten- 

 tion to the spontaneous, periodic and irritable movements of 

 leaves. Thus the so-called sleep movements are exhibited by a very 

 great number of plants. In the daytime the leaves will be 

 expanded. At night they will close in various ways. Automatic 

 and irritable movements are somewhat less widely distributed — 

 the telegraph plant is a good example of the first, the sensitive 

 plant of the second. The mechanism of all these movements 

 is essentially the same, viz. that at the base of each leafstalk or 

 leaflet there is a flexible joint usually pronounced and well 

 defined from the rest of the tissue. 



I should like to draw attention to some of the physiological 

 and morphological phenomena as displayed by one of the best 



