Alocasia watsoniana was originally published as Alocasia longiloba Miq. Alocasia watsoniana Hort. is a synonym (exoticrainforest.com). I have seen this plant listed as Alocasia watsoniana and Alocasia longiloba ‘Watsoniana’; it seems that botanists have grouped a number of previously separate species together as part of the Alocasia longiloba complex so it's probable that this plant is Alocasia longiloba ‘Watsoniana’.
Alocasia longiloba is part of the Araceae family and its native range is China (S. Yunnan, Guangdong) to W. & Central Malesia. ‘Watsoniana’ leaves are sagittate although more rounded than Alocasia longiloba, leaf blades are a glossy dark green with significantly more silver veining and purple undersides. Genus name comes from the Greek ‘a’ meaning without and ‘locasia’ meaning lotus root. The specific epithet is derived from the Latin words longus meaning ‘long’ and lobus meaning ‘a rounded projection or protuberance’ this is in reference to the lobes.
https://www.exoticrainforest.com/Alocasia%20micholitziana%20%20pc.html
Pot: ø 14cm.
Height: Approximately 35cm from base of pot.
Light: Bright indirect light, meaning the plant sees the sun for 0-4 hours per day - this could be through trees or a translucent curtain, it’s important for the plant to see the sky in order to thrive. Alocasia can handle a few hours of direct sunlight per day. Although in its natural environment Alocasia longiloba 'Watsoniana' grows in a shady spot, this would insufficient light in the home.
Water: Alocasia prefer evenly moist soil and providing that the plant is receiving adequate light, water when the top inch of mix has dried out. Before watering, aerate the potting mix with a few pokes of a skewer or blunt stick, pour water slowly over the top and allow the water to pass through the drainage holes.
Potting mix: A well draining mix composed of coco coir, perlite or vermiculite, orchid bark and worm castings.
Fertilising: Feed your plant when you water or every other watering, during the growing season or when you observe active growth. You can dilute fertiliser to half the recommended amount but never add more.
Temperature: Ideally 18-29°C.
Humidity: Alocasia would prefer higher humidity. You can increase humidity by placing the plant on a watered pebble tray or using a humidifier.
Alocasia are toxic, keep out of reach of pets and children.