398 University of California Publications in Botany [VOL. 5 



tively high, ranging from 15 to 20 C. The results, which were 

 recorded approximately fifteen hours after subjection to the gas, arc 

 given in the following table : 



TABLE 6 



Species, variety, or Amount of abscission, expressed almost entirely 



hybrid in terms of size of flowers thrown off 



N. Tabacum var. macrophylla all buds up to anthesis. 



N. Tabacum " Maryland" all flowers up to 4 or 5 days past anthesis. 



F, H154 all buds up to opening of corolla. 



F, H36 all buds and flowers. 



F,H179 all buds and flowers. 



N. glauca young buds. 



N. rustica var.? buds up to anthesis. 



N. rustica var.? buds, flowers, and fruits. 



N. Bigelovli var. Wallacei no abscission. 



N. Bigelovii "Porno" no abscission. 



N. quadrivalvis no abscission. 



N. multivalvis no abscission. 



N. Sanderae buds up to anthesis. 



N. suaveolens buds up to anthesis. 



N. plumbaginifolia buds up to opening of the corolla. 



Solanum umbelliferum ^ small buds. 



S. jasminioides buds and flowers. 



S. verbascifolium no abscission. 



S. nigrum small buds. 



lochroma tuberosa no abscission. 



Oestrum fasciculatum buds and flowers. 



Lycopersicum esculentum var. 



pyriforme no abscission. 



L. esculentum var. vulgare small buds and occasional flowers. 



Petunia hybrida no abscission. 



Salpiglossis sinuata -no abscission. 



Datura sanguineum buds and flowers. 



Salpichrora rhomboidea no abscission. 



Lycium australis - no abscission. 



As might be expected, most of these varieties react to laboratory 

 air in the same manner that they do to illuminating gas. In the case 

 of laboratory air a longer time and higher temperature is generally 

 required before the reaction occurs. All the species, with the excep- 

 tion of those which throw off only young buds, detach most of their 

 flowers when left in laboratory air overnight. If a window or two is 

 left open, allowing fresh aid to enter and at the same time lowering 

 the temperature, no abscission occurs. 



It was found that several of the species recorded above, in which 

 no abscission or very little abscission occurred, detached more flowers 

 when a larger percentage of gas was used or when subjected to 1.5 

 per cent gas for a longer time. Thus, both varieties of Lycopersicum 



