12 PERIODICAL OPENING AND CLOSING OF FLOWERS. 



Degree of temperature. Mean time of observation. 



38'75 two species April 3. 



43-25 five „ April 18. 



4775 nine 

 5225 sixteen 

 5675 fourteen 

 61-22 six 



May 18. 



June 16 



July 5. 



July 12. 



66-75 (Malva Alcea) .... July 7. 



The limits of temperature between which flowers begin to 

 open are 38-75° and 65-75°. The number of species increases 

 up to about 54-5°, and then decreases. We observe too that 

 the temperature requisite is so much the higher, as the time at 

 which the plants blow advances in the year. But since plants in 

 general, in the same degree, require a higher temperature 

 for their expansion, the position may be regarded as sure that 

 species which require a higher temperature to attain certain 

 stages of expansion awake from their sleep at a higher tem- 

 perature. 



The following table indicates the temperature at which the 

 greatest degree of expansion takes place : — 



Degree of temperature. Mean time of observation. 



47'75 Mirabilis Jalapa (night-bloomer) 



56-75 Erodium cicutarium, "1 Mr 



Lychnis vespertina (night-bloomer) j * ^ ' 



61-25 foui' species 1 



Funkia japonica (night-bloomer) . > . . Aug. 10. 



Oenothera biennis (night-bloomer) J 



65-75 three species July 2. 



70-25 eleven „ May 27. 



74-75 thirteen „ May 30. 



79-25 fifteen „ June 26. 



83 - 75 twenty „ June 29. 



88-25 thirteen „ July 13. 



97'25 Echinocactus Ottonis July 15. 



106'25 Carlina acaulis Sep. 1. 



The night-bloomers reach the maximum of expansion at from 

 47-75°— 61-25°. The day-bloomers from 79-25°— 88-25°. The 

 remaining two species are exceptional. The number of species 

 whose blossoms are fully expanded in the day increases from 

 56-75° — 83-75°; many species, however, expand under 81-25°, 

 above that temperature extremely few, and so far from the expan- 



* The temperature is given in the original according to Reaumur's 

 scale, but is here adapted to Fahrenheit. 



