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 ; spiculse 

 squamis suffulti. Sepala mucronata. 



21. Desvauxia Di-ummondiana, 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. Joseph 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, I 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 known, but the peculiar structure of that organ has not been before ob- 

 served. — Ed. 



E 2 



