Tosefta for Terumot 2:6
וְתוֹרְמִין זֵיתֵי שֶׁמֶן עַל זֵיתֵי כֶבֶשׁ, וְלֹא זֵיתֵי כֶבֶשׁ עַל זֵיתֵי שָׁמֶן. וְיַיִן שֶׁאֵינוֹ מְבֻשָּׁל עַל הַמְבֻשָּׁל, וְלֹא מִן הַמְבֻשָּׁל עַל שֶׁאֵינוֹ מְבֻשָּׁל. זֶה הַכְּלָל, כָּל שֶׁהוּא כִלְאַיִם בַּחֲבֵרוֹ, לֹא יִתְרֹם מִזֶּה עַל זֶה, אֲפִלּוּ מִן הַיָּפֶה עַל הָרָע. וְכָל שֶׁאֵינוֹ כִלְאַיִם בַּחֲבֵרוֹ, תּוֹרֵם מִן הַיָּפֶה עַל הָרָע, אֲבָל לֹא מִן הָרַע עַל הַיָּפֶה. וְאִם תָּרַם מִן הָרַע עַל הַיָּפֶה, תְּרוּמָתוֹ תְרוּמָה, חוּץ מִן הַזּוּנִין עַל הַחִטִּים, שֶׁאֵינָן אֹכֶל. וְהַקִּשּׁוּת וְהַמְּלָפְפוֹן, מִין אֶחָד. רַבִּי יְהוּדָה אוֹמֵר, שְׁנֵי מִינִין:
One should set aside <i>Terumah</i> oil olives for pickled olives but not pickled olives for oil olives, and unboiled wine for boiled wine but not boiled wine for unboiled wine. The rule is that for any species that is considered <i>Kilayim</i> [forbidden mix of two species] with another species, one should not set aside <i>Terumah</i> from one [species] for the other [species], even from the good [species] for the bad [species]. And any species that is not considered <i>Kilayim</i> with another species, one may set aside <i>Terumah</i> from the good [species] for the bad [species], but not from the bad [species] for the good [species]. But if one set aside <i>Terumah</i> from the bad for the good, his <i>Terumah</i> is valid <i>Terumah</i>, except for from darnel [a poisonous rye grass] for wheat, since [darnel] is not a food. The gourd and the cucumber are one species. Rabbi Yehudah says [they are] two species.