* Cell walls: Both plant and algae cells have cell walls, which provide structural support and protection. These cell walls are often made of cellulose, which can be quite rigid. So, in this sense, both plant and algae cells have a "hard" outer layer.
* Other structures: Some algae, like diatoms, have cell walls made of silica (glass), making them extremely hard and durable. Plant cells, on the other hand, don't have silica in their cell walls.
So, the answer depends on what you are looking for. Both plant and algae cells have cell walls, but the material and hardness of those walls vary.
