From Dubuque we took steamer up the Mississippi River, through its finest scenery up to St. Paul, Minnesota; saw the falls of St. Anthony and Minnehaha; thence, while the rest of our party essayed Lake Superior, Mrs. Gray and I returned home by rapid stages. I have only to-day finished the study and laying into the herbarium of specimens I gathered and dried, regretting the while that I did not collect more specimens and many other species, as I might have done. Tyndall is in Boston, and I trust will be with us next week. I have not yet seen him, nor Froude, nor even MacDonald, the third lecturing notability in Boston. TO CHARLES DARWIN. CAMBRIDGE, October 6, 1872. You delight me by your promise to take up Dionæa and Drosera now, and I imagine you as now about it. Good! And I am so glad you will take that opportunity to collect your botanical and quasi-botanical papers. These, with the Dionæa, etc., will make a nice and most welcome volume. In answer to your query, I think I can “support the idea,” or the probability of it, “that tendrils become spiral after clasping an object from the stimulus from contact running down them.” For though some “tendrils do become spiral when they have clasped nothing,” others do not. The adjustment of the unstable equilibrium is more delicate in the former, so that it starts under some inappreciable cause or stimulus. That the stimulus may be so propagated downward is clear in the sensitive plant, where the closing of the leaflets in succession will follow the closing of the ultimate pair under slight and local irritation. And in the tendril the coiling below is just a continuation of the same movement or same change as that which incurved the tip in clasping, that is, a relative shortening of concave or lengthening of the convex side of the tendril. Would you not infer that the action was propagated downward?