96 MR. C. DAEWIN ON THE DIMOEPHIC CONBITIOTf IN PEIMULA. 



tlie Boraginece, Prof. Gray finds a new and inexplicable case, — 

 namely, some specimens witli the stamens and pistil sub-esserted, 

 and other specimens with loth organs seated low down the tube of 

 the corolla. Dr. Torrey and Prof. Gray have designated aU such 

 plants as " diceciously dimorphous." IntheXaJiatejMr.Bentham 

 informs me that several species oiyEgiphyla, and some of Mentha, 

 are dimorphic like Primula. The case of Thymus is different, as I 

 know from my own observations ; but I will not here enlarge on 

 this genus. Again, as I hear from Mr. Bentham, numerous species 

 of Oxalis are similarly dimorphic. I can add the genus Linum. 

 So that we already know of species (generally several in the same 

 genus) having distinct dimorphic individuals, as far as structure 

 is concerned, however it may prove in function, in no less than 

 eight natural orders. 



AVith respect to Linum, I will not here enter on details, as I in- 

 tend to try further experiments next summer ; but I may state, 

 that 1 observed many years ago two forms in Linum flavmn, with 

 both the pistils and stamens differing in length. In Linum grandi- 

 florum there are likewise two forms which present no difference in 

 their male organs, but the pistil and stigmatic surfaces are much 

 longer in the one form than in the other. The short-styled form, 

 I have good reason to believe, is liighly fertile with its own pollen ; 

 whether it be more fertile with the pollen of the long-styled form, 

 I cannot at present say. The long-styled form, on the other hand, 

 is quite sterile with its own pollen : several plants grew in my 

 garden, remote from the short-styled plants ; their stigmas were 

 coloured blue with their own pollen ; but although they produced 

 a vast number of flowers, they did not produce a single seed- 

 capsule. It seemed a hopeless experiment ; but I had so much 

 confidence from my trials on Primula, tliat I put a little pollen 

 from the short-styled plants on the stigmas (already blue with 

 . their own pollen) of twelve flowers on two of the long-styled 

 plants. From these twelve flowers I got eight remarkably fine 

 seed-capsules ; the other flowers not producing a single capsule. 

 The existence of plants in full health, and capable of bearing 

 seed, on which their own pollen produces no more effect than 

 the pollen of a plant of a different order, or than so much in- 

 organic dust, is one of the most surprising facts which I have ever 

 observed. 



