RFC realization for bias of microwave transistor circuits
A 1/4 wave stub acts as a short circuit in its own right and any capacitance to ground at the "cold" end is good practice but a bonus. 

I'm not familiar with the diagram conventions - but, what are the 'oblong' and square 'blobs' (symbols) at the outboard end of the stubs (by the arrows in each case).?
If the stubs are the "tracks" from power output collector &amp; drain respectively, and if the blobs are capacitors (as they may be) then they serve the short circuiting function and Cb x 3 in the left hand diagram are primarily bias transistor emitter decoupling which also helps with any RF that gets beyond the stub. 



Added: 

The text associated with the second diagram on page 22 in this document explains the biasing feed arrangement. They say that the "track + square" symbol represents a 1/2 wave stub that is tapped at the 1/4 wave point.   

The 1/2 wave stub appears as an open circuit to the amplifier and the 1/4 wave tapping is a zero voltage point where bias is applied. In an ideal system this point has no signal present and no additional decoupling is needed. In real world situations there will (usually) be some sort of additional capacitive decoupling in the bias feed "to keep Murphy honest". 

They say -