18709. | in Natural Selection in Plants. 417. 
widely separated regions with different soils and climates to con- 
ceive of conditions which might give to Erodium a rank succu- 
‘lent and tender growth, which, continued for a few years might 
differentiate the rigid bristles and barb of its ovaries in the direc- 
tion of greater flexibility; or on the other hand to modify the 
soft nap or pile on the surface of the ovaries as well as the flexi- 
ble tip of the foreign geraniums in the direction of rigidity or 
spine-like stiffness. Those influences which induce succulent or 
ligneous tendencies in plants are to a great extent the factors in 
such variation. 
The seeds of geraniums found in the highlands of Uruguay, as 
well as the seeds of certain other plants, exhibit the same inter- 
esting peculiarities.) 
Notwithstanding the browsing of cattle the Erodium gained 
upon the previously conspicuous forms. Within the past two 
years, however, it has been losing ground, in some places more 
1 An exceedingly brief outline of this paper was read by me before the California 
Academy of Sciences, June 17th, 1878; subsequently. my friend, Mr. X. Y. Clark, 
sent me the following clipping rot Nature of March 1, 1877, which I had not pre- 
viously seen: 
"Tiy groscopic Seeds.—I have lately received an ooh ie letter from Fritz Miil- 
ler, in St. Caterina, Brazil, on the subject bad hygroscopic seeds. He tells me e 
in the highlands of the Urugu uay he Se succeeded in discovering more fins a doz 
grasses, as well as a ate of geranium, prat awns are capable of h araea 
i ma 
l 
twists on its pm pers when the eet is is dried. These tails sol ote in three directions 
ed Fri i 
parent pla . Anot] \ because 
it illustrates the explanation which "gpl re) rh: torsion of the awn of ‘Stipa, namely, 
- that each i ich the is com is capable of t a 
their combined action results in the testing of the whole awn. Now in this species 
Of Aristida each of the three tails into which the awn is divided i is capable of tor- 
sion on its own axis, and as the seed dries as So Be gene fect th GPRS 
‘= “Down, Beckenham, February 19. FRANCIS DARWIN.” 
The Transactions referred to in Mr. Darwin’s foot-note are not within my reach, 
and the article referred to by him, is unknown to me. I am curious to.learn how far 
my observations and comments, made quite independently and without knowledge 
of anything elsewhere written, may agree with or sustain previous writers, or be 
corroborated and sustained by their obseryndioes 
