y. In a short time we might earnestly wish for a centrifugal
apparatus or a heliostat. In all such cases it would make a great
difference if a man knew that he could use a particular instrument
without great loss of time. I have now given my opinion, which is very
decided, whether right or wrong, and Frank quite agrees with me. You
can, of course, show this letter to Hooker.

LETTER 746. TO F. LUDWIG. Down, May 29th, 1878.

I thank you sincerely for the trouble which you have taken in sending
me so long and interesting a letter, together with the specimens.
Gradations are always very valuable, and you have been remarkably
successful in discovering the stages by which the Plantago has become
gyno-dioecious. (746/1. See F. Ludwig, "Zeitsch. f. d. Geo. Naturwiss."
Bd. LII., 1879. Professor Ludwig's observations are quoted in the
preface to "Forms of Flowers," Edition II., page ix.) Your view of its
origin, from being proterogynous, seems to me very probable, especially
as the females are generally the later-flowering plants. If you can
prove the reverse case with Thymus your view will manifestly be rendered
still more probable. I have never felt satisfied with H. Muller's view,
though he is so careful and admirable an observer. (746/2. See "Forms
of Flowers," Edition II., page 308. Also letter 744.) It is more than
seventeen years since I attended to Plantago, and when nothing had been
published on the subject, and in consequence I omitted to attend to
several points; and now, after so long an interval, I cannot pretend to
say to which of your forms the English one belongs; I well remember that
the anther of the females contained a good deal [of] pollen, though not
one sound grain.

P.S.--Delpino is Professor of Botany in Genoa, Italy (746/3. Now at
Naples.); I have always found him a most obliging correspondent.

LETTER 747. TO W. THISELTON-DYER. Down, August 24th [1878].

Many thanks for seeds of Trifolium resupinatum, which are invaluable to
us. I enclose seeds of a Cassia, from Fritz Muller, and they are well
worth your cultivation; for he says they come from a unique, large and
beautiful tree in the interior, and though looking out for years, he
has never seen another specimen. One of the most splendid, largest and
rarest butterflies in S. Brazil, he has never seen except near this
one tree, and he has just discovered that its caterpillars feed on its
leaves.

I have just been looking at fine young pods bene