deceased son's property can be transferred in mother's name

As per Section 8 of Hindu Succession Act 1956, The property of a Hindu Male dying intestate shall devolve firstly upon the heirs being relatives specified in Class I of the schedule. Mother comes in Class I heirs of the schedule. So, the property of a deceased son can be transferred in mother's name, if no will is made. You will have to initiate  procedure for grant of letter of administration under by filing petition under section 278 of Indian Succession Act 1925.

Dear Sir 

Since your son was unmarried therefore the immediate heir to his propety would be you and your wife.  heirs can draw a family settlement deed where each member signs, which can then be registered for official records. To transfer property, you need to apply at the sub-registrar's office. You will need the ownership documents, the Will with probate or succession certificate.