Mr. Henderson on the Stigma in Mimulus and Diplacus. 51 
20. Leptocarpus spathaceus, R. Br. Distinctum genus. Stylus tri- 
gonus, crassus ; ovarium triangulare, in stylum decurrens. Flores 
fasciculati (quos dicunt) terni quaterni, capituliformes ; spicule 
squamis suffulti. Sepala mucronata. 
21. Desvauxia Drummondiana, N. ab E., receptaculo subpaleaceo, 
stylis 6—7 basi connatis valvulis asperis infra apicem obtusum 
aristato-mucronatis mucrone valvula sua duplo breviori, foliis 
capillaribus scabris scapo glabro brevioribus. 
D. Billardieri, R. Br. affinis. 
VI.—On the Structure of the Stigma in Mimulus and Dip- 
lacus. By Mr. JosevH HENDERSON. 
To Richard Taylor, Esq. 
Sir, 
I HAVE observed a very singular instance of irritability in the 
stigmata of some species of Mimulus and of one species of 
Diplacus, a genus recently separated by Nuttall from Mi- 
mulus. As I have nowhere seen any mention made of the 
existence of the phenomenon of irritability in any of these 
plants, you will perhaps favour me, should the fact not have 
been before observed, by inserting this notice in the Annals of 
Natural History *. 
_ In making an experiment to ascertain if Diplacus puniceus 
would hybridize with Mimulus cardinalis, 1 found on apply- 
ing the anther of the latter to the bilamellate stigma of the 
former, that the plates—which in their natural position are 
reflexed—immediately collapsed, and inclosing the mass of 
pollen grains that had fallen on them, pressed firmly against 
each other. The intimate connexion-between the genus Dip- 
lacus and Mimulus, induced me to try if this unexpected pro- 
perty existed also in stigmata of the latter genus, and I found 
it to be present in Mimulus cardinalis, roseus, luteus and mos- 
chatus, all the species of Mimulus growing here. The move- 
ment in all these cases follows the touch as rapidly as in Mi- 
mosa pudica; the stigma, however, is more active when the 
flower is first opened. If the stigma is touched with a pin or 
any other instrument, the plates, after collapsing, will revert 
to their natural position, generally in less than two hours; but 
if pollen is interposed between the plates, they remain closed 
a much longer time. 
In the 27th Number of the Annals of Natural History there 
is a note on the movement of the style of Goldfussia aniso~ 
phylla by Professor Morren of Liege, in which he refers the 
* The excitable property of the stigma of Mimulus and Diplacus is a fact 
well reste} but the peculiar structure of that organ has not been before ob- 
served.—Ep. 
E 2 
