functions . php fatal error line 326

I have just tried posting to my blog and have the following error. Can anybody help me understand this please.

Fatal error: Allowed memory size of 16777216 bytes exhausted (tried to allocate 218754 bytes) in /home/abcd/public_html/wxyz/wp-includes/functions.php on line 326

This is the content of the functions file lines 322 – 329

function maybe_serialize($data) {
	if ( is_string($data) )
		$data = trim($data);
	elseif ( is_array($data) || is_object($data) )
		return serialize($data);
	if ( is_serialized($data) )
		return serialize($data);
	return $data;
}