Hi Mr. Worsley-Beiiison on tJw 



known as that of the movements of leaves ; but it was probably 

 connected with the contractile power of protoplasm in the 

 attached parts of their organs, and with variation in turgescence. 

 Moisture governed some of the floral movements of hygroscopic 

 plants, and thus meteorological changes might often be predicted 

 with tolerable accuracy. The Siberian sow-thistle closed at 

 night if the following day was going to be fine, and the reverse ; 

 bindweed, marigold, and j)impernel, if open, closed on the 

 approach of rain. Many leaves were hj'grometric, as were also 

 some larger J/r/^r. Of flowers, the pimpernel, or " poor man's 

 weather-glass," was most reliable, keeping its petals closed if 

 clouds were coming, open if a fine day was at hand. If pim- 

 pernel was wide open at 9 a.m., the day was almost sure to be 

 fine. The time of year at which flowers opened was, Mr. 

 Worsley-Benison said, governed by the intennitu of the light. 



Plants forming their floral buds in the autumn, and opening 

 in the spring, were usually short-flowered ; those budding and 

 expanding in the same year mostly remained open longer. So 

 with geographical difi'erences, a plant opening at 6 a.m. in 

 Senegal, did not open in England until 8 or 9 a.m., and in 

 Sweden not until 10 a.m. One opening in Senegal at 10 a.m., 

 opened in England at noon, and not at all in Sweden ; and one 

 opening at noon in Senegal, would not bloom either in England 

 or in Sweden. Forced plants, acted on by artificially increased 

 light and heat, as hot-house and stove plants, and those grown 

 in electric light, were similarly affected. 



Heliotropism was the turning either towards or away from the 

 light. Positive heliotropism, or turning towards the sun, a 

 common occurrence, was seen in the internodes of growing 

 stems, in petioles, and in flower-stalks. This was caused by the 

 part turned to the light, the concave side, being retarded in 

 growth ; the convex side, or part turned away from the light, 

 growling more rapidly. Among flowers, the Coinpndta: furnished 

 many examples. In particular, the peduncle of the sunflower 

 twisted in a circle during the day, bringing its flower constantly 

 towards the sun. The flower usually faced south-east, and 

 when the petioles became etiolated, the twisting came into 

 action. Piipening corn inclined to the south, not to the north. 

 Negative heliotropism, the turning away from the light, was a 

 rarer phenomenon, and was the reverse of the above. The part 

 exposed to the sun grew more rapidly, and being convex, the 

 concave side was turned away from the sun. Examples were 

 attbrded by the older branches of the ivy and the tendrils of 

 vines, also in the tendrils of Bvinonia, and the moving masses of 

 AL,thaliuin. In the cyclamen it enabled the plant to scoop a hole 

 with its peduncle in tlie eaitli or sand, and bury its own seeJ- 

 pods. An allied phenomenon was seen in the compass-plant of 



