Briefly summarized, the facts are as follows: The defendant has been a tenant in the premises in question for a period of approximately four years. The tenancy is a parol month to month tenancy, running from the first day of the month for a monthly rental of $80. The evidence demonstrates nothing remarkable until on or about July 1, 1974, when the plaintiff, landlord, hand delivered a letter to the defendant which gave him notice of a rental increase to $100 commencing on August 1, 1974. The defendant refused to accept the increase and offered checks, in the amount of $80 each, to the plaintiff on the first days of August, September, and October. Each check bears the defendant's notation on its face that it is rent for the period stated. There are other checks for successive months thereafter which are not relevant to the issue.