If a bill presented to the Governor contains an item or several items of appropriation, he may object to one or more items while approving other portions of the bill. In such case he shall append to the bill, at the time of signing it, a statement of the items to which he objects, and the reasons therefor. If the Legislature is in session, the Governor shall transmit to the house in which the bill originated a copy of the statement. The items so objected to shall be separately reconsidered in the same manner as bills which have been disapproved by the Governor.