this is a colloquial phrase that we use to emphasize the previous point. here's an example: A: we were really busy at work today B: yeah, I know. A: no, seriously. I didn't even get to take any breaks so in this example, although person B agrees that it was busy, person A adds "no seriously" to emphasize just how busy it was. *it doesn't really matter whether person B agrees or disagrees with person A, it can be used any time you want to add extra emphasis on the previous statement. example: A:This class is so hard! B: I don't think it's that bad A: No, seriously! I took chemistry last semester and it wasn't as hard as this class.

no seriously = the first sentence was very ironic. Look at it again, and you'll see.

It means that the person is speaking truthfully to you and not joking. Mike: Is physics class hard? Fred: Yes. Mike: But is it really hard, or just a lot of homework? Fred: Seriously, it is the most difficult class I have ever taken. We use this word all the time, seriously!

There is a comma after the "no". The meaning of the "no" is "all kidding aside".

In this use, "No, seriously" is used to affirm the person's statement that the mums look stunning. I usually say this, when there is could be some doubt about my statement..