PI,ANT BREEDING I271 



Giant plants are explained by means of the theory of Tschermak on 

 the association and dissociation of " cry ptomerous factors". According to 

 this theor>% the races which from time to time produce giant plants are 

 forms with dissociated cryptomerous inherited factors, that is to say that 

 the factors which transmit the height of the plants, the standard of size, 

 the number and distance apart of the leaves, the period of growth, etc., 

 are combined in such a way with the factors which transmit the abnormal 

 height, many leaves and a longer period of vegetation, that there is no action 

 of the one class of factors on the other under ordinary conditions. The cha- 

 racters of the giant plant being dissociated from those of the normal plant 

 therefore remain under these cryptomerous conditions, and a normal plant 

 is formed. If, however, owing to external circumstances the two catego- 

 ries of factors come into contact, then in the progeny giant plants in greater 

 or lesser number form according to the intimacy of this contact. 



The property which produces the giant is therefore made up of several 

 factors : slow growth, indefinite growth of the main axis (leader), poor in- 

 florescence, long period of vegetation, leaves much more numerous, less wide, 

 etc. Each of these factors is presumed to be present in the normal plant, 

 but dissociated from the normal factors, for which reason they have no in- 

 fluence on each other. If a partial association occurs, a transitional form 

 results. For instance, if the factor for late flowering remains dissociated, 

 then the giant plant flowers like an ordinary plant ; if the factor for slow 

 g'rowth remains dissociated, the plant develops as rapidly as a normal 

 plant ; if, finally, the factors of an indefinite growth and of a defective 

 inflorescence remain dissociated, there is only obtained a plant with many 

 leaves of less width and smaller internodes, which for the rest, however, 

 present nothing abnormal. A perfect association therefore produces giant 

 plants exclusively, and a complete dissociation furnishes only ordinar}^ 

 plants. 



Following the example of R. ThOMAS, Bateson, G. Howard and Fru- 

 WIRTH, the writer also made experiments on parthenogenesis in tobacco. 

 The negative results which he got invalidate those of R. Thomas and Ba- 

 teson and confirm those of G. Howard and Fruwirth (i). 



All growers know how frequent are anomaUes in the tobacco plant. 

 The writer found golden-yellow types and others which were variegated in 

 every degree ; there is often fasciation of the stem and epiascidia and hypo- 

 ascidia occur in the leaf. 



Tobacco seeds kept in airtight bottles retain their germination capacity 

 in the tropics for 7 years at least. Germination experiments undertaken 

 to elucidate the question whether the specific gravity affects the germina- 

 tion rapidity and capacity have shown that seeds which float in a solution of 



(i) Continuining these investigations the writer has since obtained positive results. A Ja- 

 panese race '', Okonawa ", with white llowers, shjuly leaves and very lengthy period of vegct;i- 

 tion produced fruits and seeds withcjul pollination. The fruits are perfectly normal, but the 

 seeds have not yet been studied. It this may not be a delinite case of true parthenogenesis at 

 any rate the seeds have well developed inlegumenl. 



