Adventure Comics (1938) 315-A

Tales of the Legion of Super-Heroes in "The Legionnaire's Super Contest" and "The Winner of the Super-Tests!"
*In saving Earth from a band of space-raiders, the Substitute Legion inadvertently reveals its existence to the Legion of Super-Heroes. When they explain that they exist not as competition but as secret helpers, the members are invited to participate in a series of contests, the winner to be made a full Legionnaire.

Polar Boy enters a volcano, and uses his powers to safely thaw a pair of frozen scientists; Night Girl vanquishes Sun Woman, the tyrant of Vannar; Chlorophyll Kid splits a mountain by accelerating the growth of plants within it to create a needed water passage; and Fire Lad creates a permanent fire-geyser on a rainy asteroid. Only Stone Boy fails in his task to subdue and capture a wild beast, but because only he refuses to try a second time for fear that the beast might hurt someone. The Legionnaires are impressed enough with his show of self-sacrifice to choose him as winner. Stone Boy is grateful for the honor, but decides to stay with his friends in the Substitutes. *Source: The Official Legion of Super-Heroes Index #2 - Published by ICG.

"Your Free Trip Around the World"

Superboy in "The Titanic Boy of Steel"
After being exposed to Red Kryptonite, Superboy grows to giant-size. Colossal Boy helps him conceal his secret identity as Clark Kent from Lana Lang.