Cameron Davidson-Pilon 
Though not the traditional way to propagate, you can use submerged or liquid cultures to grow molds and fungi. This has been a recent change in mushroom propogation too: more and more groups are moving from agar plates to liquid cultures. How does it work? A nutrient broth is prepared with water, minerals, and a carbon source and steralized in a pressure cooker / autoclave. A syringe is inserted that is filled with an existing liquid culture and expelled. Simple as that. The fungi will start to consume the nutrients and grow whispy mycellium. In fact, there are companies that are taking advantage of the now-easily-isolated mycellium and turning them fibers for plant-based meats. For example, Prime Roots is using our fermentation friend Aspergillus oryzae for exactly this. That’s right, you can grow koji in water! Tempeh (Rhizopus oryzae), too. Here’s a microscopic video of my submerged tempeh culture, at 1000x magnification:
Rhizopus oryzae at 1000x in a liquid culture. If you zoom in, you can see movement inside the microbe