212 THE FLOWERING PROCESS 



»^ 23. Short-day plants at high temperature; day-neutral at low: no direct 

 effect. It is interesting that the last two examples should fall in the same 

 category. Maryland Mammoth tobacco was the first plant shown to have 

 a short-day requirement, and a study of the flowering of this plant led to 

 the discovery of photoperiodism. The Japanese morning glory is one of 

 the newest plants studied by plant physiologists, and yet it has been 

 studied almost more extensively than the tobacco, or any other plant for 

 that matter. 



Chenopodium album. Fig. 3-8 Pigweed variety 



Nicotiana Tabacum, H. 66, C. 198 Maryland Mammoth 



tobacco 

 Pharbitis Nil, Ogawa, Y., 1960, Bot. Japanese morning glory, 

 Mag. {Tokyo), 73 : 334-335 ; Takimoto, var. violet 



A., Tashima, Y., and Imamura, S., 1960, 

 Bot. Mag. {Tokyo), 73: 377, Fig. 1-C 



.QJ| 24. Short-day plants at high temperature; long-day plants at low; no 

 ^^ causative effect. Such a complete change in response type provides a very 

 striking category. 



Euphorbia pulcherrima, H. 96 Poinsetta 



Ipomoea purpurea, H. 91 Morning glory 



10 25. Short-day plants promoted by high temperature. 



Cosmos sulphureus, H. 80 Klondike cosmos 



Chrysanthemum morifolium, C. 214, 218 Variety 5 

 Oryza sativa, H. 39 Winter rice 



t #^ 26. Short-day plants promoted by high temperature; critical dark period 

 inversely proportional to temperature. 



Glycine soja, H. 61, Fig. 1-D Soybean, Biloxi 



Viola papilionacea ? H. 102 Violet 



1 9 27. Short-day plants; require low temperature. This is also a significant 

 category, since many workers have felt that only long-day plants might 

 have a low temperature requirement. 



Chrysanthemum morifolium, C. 214, 218 Variety 6 



• O 28. Long-day plants; no direct effect of temperature. It is quite likely that 



a number of these might display a temperature interaction if investigated 

 in the proper way. 



Agropyron smithii, H. 53 Wheatgrass 



Agrostis nebulosa, H. 32 Cloudgrass 



Agrostis palustris, H. 26 Bentgrass 



Alopecurus pratensis, H. 35 Foxtail 



Anagallis arvensis, C. 218 Pimpernel 



Anethum graveolens, H. 10, C. 203 ? Dill 



Avena sativa, H. 36 C. 197 Oat 



Chrysanthemum frutescens, H. 75 Paris daisy 



Chrysanthemum Leuchanthemum, H. 106 Ox-eye daisy 



Dianthus superbus, C. 212, 218 Carnation 



Festuca elatior, H. 34 Fescue 



Hibiscus syriacus, H. 68 Althea 



Lolium temulentum, Evans, L. T., 1958, Ryegrass (induced by a 

 Nature, 182: 197-198 single cycle) 



