The seeds were sown, and in turn yielded plants which when self-fertilized gave four kinds of seeds (which frequently all appeared in the same pod). Thus 556 seeds were produced by 15 plants, having the following characters:— _AB_ 315 round and yellow _Ab_ 101 angular and yellow _aB_ 108 round and green _ab_ 32 angular and green These figures stand almost in the relation of 9 : 3 : 3 : 1. These seeds were sown again in the following year and gave:— From the round yellow seeds:— _AB_ 38 round and yellow seeds _ABb_ 65 round yellow and green seeds _AaB_ 60 round yellow and angular yellow seeds _AaBb_ 138 round yellow and green, angular yellow and green seeds From the angular yellow seeds:— _aB_ 28 angular yellow seeds _aBb_ 68 angular yellow and green seeds From the round green seeds:— _Ab_ 35 round green seeds _Aab_ 67 round angular seeds From the angular green seeds:— _ab_ 30 angular green seeds Thus there were 9 different kinds of seeds produced. There had been separated out at this time 38 individuals like the parent seed plant, _AB_, and 30 like the parent pollen plant, _ab_. Since these had come from similar seeds of the preceding generation they may be looked upon as pure at this time. The forms _Ab_ and _aB_ are also constant forms which do not subsequently vary. The remainder are still mixed or hybrid in character. By successive self-fertilizations it is possible gradually to separate out from these the pure types of which they are compounded. Without going into further detail it may be stated that the offspring of the parent hybrids, having two pairs of differentiating characters, are represented by the series:— _AB_ _Ab_ _aB_ _ab_ 2_ABb_ 2_aBb_ 2_Aab_ 2_ABa_ 2_AaBb_ This series is really a combination of the two series:— _A_ + 2_Aa_ + _a_ _B_ + 2_Bb_ + _b_ Mendel even went farther, and used two parent varieties having three differentiating characters, as follows:— _ABC seed parent_ _abc pollen plant_ { A form round { a form angular { B albumen yellow { b albumen green { C seed-coat grey { c seed-coat white brown The results, as may be imagined, were quite complex, but can be expressed by combining these series:— _A_ + 2_Aa_ + _a_ _B_ + 2_Bb_ + _b_ _C_ + 2_Cc_ + _c_