GYNO-DIOECIOUS PLANTS.
The plants hitherto described either show a tendency to become dioecious, or apparently have become so within a recent period. But the species now to be considered consist of hermaphrodites and females without males, and rarely show any tendency to be dioecious, as far as can be judged from their present condition and from the absence of species having separated sexes within the same groups. Species belonging to the present class, which I have called gyno- dioecious, are found in various widely distinct families; but are much more common in the Labiatae (as has long been noticed by botanists) than in any other group. Such cases have been noticed by myself in Thymus serpyllum and vulgaris, Satureia hortensis, Origanum vulgare, and Mentha hirsuta; and by others in Nepeta glechoma, Mentha vulgaris and aquatica, and Prunella vulgaris. In these two latter species the female form, according to H. Muller, is infrequent. To these must be added Dracocephalum Moldavicum, Melissa officinalis and clinopodium, and Hyssopus officinalis. (7/14. H. Muller 'Die Befruchtung der Blumen' 1873 and 'Nature' 1873 page 161. Vaucher 'Plantes d'Europe' tome 3 page 611. For Dracocephalum Schimper as quoted by Braun 'Annals and Magazine of Natural History' 2nd series volume 18 1856 page 380. Lecoq 'Geographie Bot. de l'Europe' tome 8 pages 33, 38, 44, etc. Both Vaucher and Lecoq were mistaken in thinking that several of the plants named in the text are dioecious. They appear to have assumed that the hermaphrodite form was a male; perhaps they were deceived by the pistil not becoming fully developed and of proper length until some time after the anthers have dehisced.) In the two last-named plants the female form likewise appears to be rare, for I raised many seedlings of both, and all were hermaphrodites. It has already been remarked in the Introduction that andro-dioecious species, as they may be called, or those which consist of hermaphrodites and males, are extremely rare, or hardly exist.
Thymus serpyllum.
The hermaphrodite plants present nothing particular in the state of their reproductive organs; and so it is in all the following cases. The females of the present species produce rather fewer flowers and have somewhat smaller corollas than the hermaphrodites; so that near Torquay, where this plant abounds, I could, after a little practice, distinguish the two forms whilst walking quickly past them. According to Vaucher, the smaller size of the corolla is common to the females of most or all of the above-mentioned Labiatae. The pistil of the female, though somewhat variable in length, is generally shorter, with the margins of the stigma broader and formed of more lax tissue, than that of the hermaphrodite. The stamens in the female vary excessively in length; they are generally enclosed within the tube of the corolla, and their anthers do not contain any sound pollen; but after long search I found a single plant with the stamens moderately exserted, and their anthers contained a very few full-sized grains, together with a multitude of minute empty ones. In some females the stamens are extremely short, and their minute anthers, though divided into the two normal cells or loculi, contained not a trace of pollen: in others again the anthers did not exceed in diameter the filaments which supported them, and were not divided into two loculi. Judging from what I have myself seen and from the descriptions of others, all the plants in Britain, Germany, and near Mentone, are in the state just described; and I have never found a single flower with an aborted pistil. It is, therefore, remarkable that, according to Delpino, this plant near Florence is generally trimorphic, consisting of males with aborted pistils, females with aborted stamens, and hermaphrodites. (7/15. 'Sull' Opera, la Distribuzione dei Sessi nelle Piante, etc' 1867 page 7. With respect to Germany H. Muller 'Die Befruchtung etc.' page 327.)
I found it very difficult to judge of the proportional number of the two forms at Torquay.