4 adjectives to describe alternating

Grave alternates with gay: now serious converse, and now jokes, anecdotes, and playful raillery.

The idyllic manner alternates with the satiric, the pathetic, even the sublime, by such imperceptible gradations, and continual delicate variations of key, that the harmonious medley of his style becomes the fit outward expression of the bizarre and yet harmonious fairyland in which his fancy ranges.

The stem is also indistinctly divided into internodes, from each of which a single pinna is given off alternately on opposite sides, and besides the pinnae there are three cells on each internode, two on the side from which the pinna springs, and on the opposite side alternate in position to the other two.

With the Dutch fashions came in Flemish bond, in which, in each course, a header and a stretcher alternate.

4 adjectives to describe  alternating