27. 61.] TO CHARLES DARWIN. 631 
River, through its finest scenery up to St. Paul, Min- 
nesota; saw the falls of St. Anthony and Minne- 
haha; 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 speci- 
mens 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 Dio- 
nea 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 Dionea, ete., will 
make a nice and most weleome 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 stimu- 
lus 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 pro- 
pagated downward is clear in the sensitive plant, 
where the closing of the leaflets in succession will fol- 
low the closing of the ultimate pair under slight and 
