490 LIFE MOVEMENTS IN PLANTS 



electric probe is definitely found to be the endodermis con- 

 taining large sized starch grains. 



INFLUENCE OF SEASON ON OEO-ELECTRIC RESPONSE. 



I vshall now describe certain modifications in responst^, 

 which result from the change of season and also from 

 condition of high temperature. Physiological reactions, 

 generally speaking, are much affected by different seasons ; 

 thus the seedlings of Scirpus Kijsoor exhibit a very rapid 

 rate of growth of 3 mm. per hour in August, but a 

 month later the growth-rate declines to only 1 mm. per 

 hour. I find similar depression of growth with the ad- 

 vance of season in si^edlings of Zea Mays, where a very 

 rapid fall in growth takes place in the course of a fort- 

 night. The intensity of geotropic responses, both mechanical 

 and electrical, of Tropceohim declines rapidly in the course 

 of a month from February to March (p. 454). The fiowers 

 of Nymplioea began to appear by the end of June when 

 the flower stalks exhibited strong geo-electric response. But 

 later in the season, by July and the beginning of August, 

 the response underwent continuous decline, and by the end 

 of August the response was nearly abolishetl. 



Much time had to be spent in perfecting the appara- 

 tus, and it was not till the beginning of August 

 that the investigations could be properly started ; the res- 

 ponsive indications were, however, marked and definite, 

 though relatively feeble compared to those obtained at the 

 beginning of the season. The decline of the geo-electric 

 response was to a certain extent also due to the prevailing 

 high temperature. 



Effect of high temperature. — I shall in the next chapter 

 describe experiments which show that geotropic response 

 is diminished under rise of temperature. The specimens 

 employed for localisation of geo-perceptive layer exhibited, 

 as stated before, a decline of geo-electric response with 



