Section 15. The governor shall annually issue a proclamation setting apart the last Friday in April as Arbor and Bird Day, recommending its observance by the public in the planting of trees, shrubs and vines, particularly those attractive to birds, in the promotion of forest growth and culture, in the adornment of public and private grounds, places and ways, and in such other efforts and undertakings as shall harmonize with the general character of the day. He shall further recommend that such day be observed in rural and suburban schools by exercises appropriate to Arbor and Bird Day.