Final answer:
The question seems to be about a German botanist who continued the work of someone named River, possibly a confusion with a figure from botany history. Noteworthy in this context is Matthias Schleiden, who, in collaboration with Theodor Schwann, developed the cell theory, recognizing cells as the fundamental unit of life in plants and animals.
Step-by-step explanation:
The question appears to ask about the discoveries made by a German botanist who continued the work of William H. River, though there's a lack of clarity about the individual's identity. Given the general context of botany and plant discovery, it's worth noting the contributions of German botanist Matthias Schleiden, who worked around a similar timeframe to that of English botanists. Schleiden, along with Theodor Schwann, was instrumental in developing the cell theory, affirming that cells are the basic units of both plant and animal life.
While not directly continuing River's work, Schleiden's advancements in botany and cell theory created a fundamental understanding of plant biology that influenced all subsequent research in the field. His microscopic observations of plant tissues helped establish botany as a rigorous scientific discipline.