LEDs are current driven, that means that they are rated at some current, say 30mA. The volt drop across any one LED might vary a bit about 2.2V, so if they are connected all in parallel as in the first figure, it is likely that one LED will "hog" too much current and be very bright, the others might be very dim (or out!). Likewise if the transistor turns on properly it will drop .2 of a volt across, giving the LEDs 3.6 - .2 = 3.4V which is too much for most sorts of LEDs. For a circuit to work and the LEDs to have a long life, they need about 2.2 V at 30mA (or what ever their rating is) so 3.4 - 2.2 volts must be dropped across a resistor. So 1 Volt at 30mA = 1000/30 ohms~33 ohms should be put in series with each LED.
Frank