1. The Gemara explains how the punishment of the generation of the Great Flood was measure for measure.
2. The Beraisa teaches the d'Rabanan law of Ma'aser for vegetables before it mentions the Torah law of Ma'aseros.
3. The Mishnah does not state that the new year is for Ma'aseros according to Torah law.
4. The new year for Ma'aser of vegetables is determined by when the vegetables are harvested.
5. Ma'aser Ani is given instead of Ma'aser Sheni in the third and sixth years of the Shemitah cycle.
A BIT MORE
1. Since they altered the normalcy of their actions, Hashem altered the constellations to punish them. Similarly, since they sinned with the heat of their passion by engaging in illicit relations, they were punished with the heat of boiling waters.
2. This is because the Tana wanted to show a fondness for Rabbinic law.
3. This is because the Mishnah understands that if it only says that this is the new year for Ma'aser d'Rabanan of vegetables, then it certainly must be the new year for the Ma'aseros that are separated according to Torah law.
4. If a vegetable is harvested right before Rosh Hashanah, it may not be separated as Ma'aser for a vegetable harvested right after Rosh Hashanah, even though they were both ready to be picked before Rosh Hashanah.
5. There is a dispute in the Gemara about the source that Ma'aser Rishon is always given, even during the third and sixth years of Shemitah.