1914] on Plant-Autographs and their Revelations ll).> 



for these particular plant-tissues have the power of storage. In this 

 way. energy derived in various ways from without — such as light, 

 warmth, food, and so on — is constantly being accumulated. When 

 a certain point is reached, there is a bubbling overflow ; and we call 

 this overflow spontaneous movement. Thus what we call automatic 

 is really an overflow of what has previously been stored up. When 

 this accumulated energy is exhausted, then there is also an end of 

 spontaneous movements (Fig. 18). But a fresh accession of stimulus 

 from outside renews these pulsations. 



In the matter of these so-called spontaneous activities of the 

 plant I find that there are two distinct types. In one the overflow 

 is initiated witli very little storage, but here the unusual display of 

 activity soon comes tc a stop. To maintain such specimens in the 



Fig. 18. — Gradual Stoppage of Pulsation in^ an 

 Isolated Desmodium Leaflet due to Run- 

 down OF Stored Energy. 



rhythmic condition, constant stimulation from outside is necessary. 

 Plants of this type are extremely dependent on outside influences,, 

 and when such sources of stimulus are removed they speedily come 

 to an inglorious stop. Averrhoa is an example of this kind. In 

 the second type of automatic plant-activity I find that long-continued 

 storage is required before an overflow can begin. But in this case 

 the spontaneous outburst is persistent and of long duration, even 

 when the plant is deprived of any immediately exciting cause. 

 These, therefore, are not so obviously dependent as the others oa 

 the sunshine of the world. Our telegraph-plant, Desmodium, is an 

 example of this. 



Instajxtaxeous Record of Growth. 



As a further example of automatic activity we may take the 

 phenomenon of growth. The rate of growth is so extremely slow 

 that even the proverbial pace of the snail is two thousand times 

 quicker : It would take an average plant two hundred years to- 

 co ver the short distance of a mile. This extreme slowness is a 



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