The Mode of Inheritance of Semi-Sterility 

 in the Offspring of Certain Hybrid Plants. 



i{y John Helling, 



Flovidii Agricultural Kxperiinent Statiou. 

 (Eingf'gaiigi'ii am 14. Felnuai' l'.il4.) 



The problem of roiiiplete or partial sterility in plant crosses is a 

 complex one, inchuliiig', inter alia, incompatibility, self-sterility, sterility 

 due to environment, steiility due to g'enetic factors affecting- the zygote, 

 abortion of micros]iore or nieoas|)ore mother-cells ("gouotokonts" of Lotsy), 

 and abortion of a fiaction of the young poUen-graius and embryo-sacs. 

 It is this last kind of partial sterility which is the subject of 

 this paper. [A similar partial abortion of gametes occurs in the ani- 

 mal kingdom in the male progeny of a Cavia species cross investigated 

 in a remarkably thorough manner liy Detleksen (4)]. in some cases 

 the fraction of pollen-grains and endii'yo-sacs which are noi'iiial approxi- 

 mates one-half; in others, it is a smaller amount. Tiie incidence of this 

 partial sterility is mainly subscMjuent to the formation of tt^trads. 



There is a considerable amount of evidence as to the alioition of 

 a fraction of the pollen-giains and embryo-sacs in hybrids and other 

 plants. (Most of the following investigators have given excellent accounts 

 of the behavior of the chi'omosomes and cytoplasm, but we are only 

 specially concerned here with the fate of the tetrads.) 



JUEL (9), in a hybrid lilac (SyriiKja chinensis) whiidi had nearly 

 all its pollen-grains abortive, found that most of the abortion took place 

 after the formation of tetrads. TISCHXER (Ki), investigating this same 

 hybrid, found abortive euünyo-sacs with only a small cavity, or with 

 none. Tischlee also determined in a hybrid cuii'ant (Ribcs Intermedium), 

 which, Janczewski stated, had only one-eighth (10 — 1.5 per cent) of its 

 pollen-grains good, that the formation of pollen tetrads was normal (17). 

 Again, Tisohlek (16, 17) found in another hybrid currant (Rihes gov- 



