Australian Finger Lime | Yellow
Citrus australasica
 
The finger lime has been recently popularised as a gourmet bushfood. The globular juice vesicles (also known as pearls) have been likened to a "lime caviar", which can be used as a garnish or added to various recipes. The fresh vesicles have the effect of a burst of effervescent tangy flavour as they are chewed. The fruit juice is acidic and similar to that of a lime and are available in white, yellow, red.
 
Seedling (nb: images are mature fruit).