No. 605] 



NUCLEUS AND CYTOPLASM 



289 



The evidence and a criticism of parts of it follows : 



1. Shull's Evidence 

 (a) Cases of maternal inheritance. Under this head- 

 ing Shull places such experiments as those of Correns 

 (1909) on Mirabilis jcdapa var. albomaculata. This plant 

 —the common fonr-o 'clock— has variegated leaves, green 

 and white, the white being due to inhibited development 

 of green in the chroniatophores. The amount of green 

 and white varies in different plants and furthermore 

 whole branches may be green while otiier whole branches 

 may be white. Flowers borne upon green branches, if 

 self-fertilized, give seed that ])roduces only green off- 

 spring. P'lowers from white bi-niiclics. it' scltVd, give seed 

 that produces only whites, wliicli dit^ iKM-aiise they are 

 unable to carry on i)hotosyiillu'si>. I'lowei-s on vari- 

 egated branches yieUi offspring some of which are green, 

 some variegated. Crosses among these green, wliite and 

 variegated plants reveal the fact that the offspring re- 

 seml)k^ invariably the female parent. White females pol- 

 linat(Ml by any green or varie-atcd poHen yield (mly 

 whit- which dh". (irroii i-vnvA\v> iM,irniattMl l)y whito or 

 varir-atcd pnlh.ii > iold oiil> urcni df^.-nidatit^. The 

 l)at(>rnal characloi' iicxcr rc;i pi H-a r^ in hiIim .iiiciil gen- 

 erations. 



Correns lia- ;i--iiiii(m1 in (.\|.laiiiiiig tlio-c roiiia rkable 

 occurrences thai a disease transmitted hy the cytoplasm 

 of the ovule is the cause of the color differences, inasmuch 

 as the white color in either self condition or as mottling 

 on the green is a ])athological condition. The chromo- 

 somes are assumed to be immune to this disease. If the 



