OCR Text |
Show 306 GYNO-DICECIOUS PLANTS. CHAP. VII. are short; the anthers do not contain any sound pollen-grains, but in their place yellow incoherent cells which do not swell in water. Some plants were in an intermediate condition; that is, had one or two or three stamens of proper length with perfect anthers, the other stamens being rudimentary. In one such plant half of one anther contained green perfect pollen-grains, and the other half yellowish-green imperfect grains. Both forms produced seed, but I neglected to observe whether in equal numbers. As I thought that the state of the anthers might be due to some fungoid growth, I examined them both in the bud and mature state, but could find no trace of mycelium. In 1862 many female plants were found; and in 1864, 32 pln.nts were collected in two localities, exactly half of which were hermaphro· elites, fourteen were females, and two in an intermediate con· clition. In 1866, 15 plants were collected in another locality, and these consisted of four hermaphrodites and eleven females. I may add that this season was a wet one, which shows that the abortion of the stamens can hardly be due to the dryness of the sites where the p·lants grew, as I at one time thought pro· bable. Seeds from an hermaphrodite were sown in my garden, and of the 23 seedlings raised, one belonged to the intermediate form, all the others being hermaphrodites, though two or three 0f them had unusually short sta1nens. I have consulted several botanical works, but have found no record of this plant varying in the manner here described. Planta,qo lanceolata (Plantaginere).-Delpino states that this plant presents in Italy three forms, which graduate from an anemophilous into an entomophilous condition. According to H. Muller,* there are only two forms in Germany, neither of which show any special adaptation for insect fertilisation, and both appear to be hermaphrodites. But I have found i~ ~wo localities in England female and hermaphrodite forms ex1stmg together; and the same fact has been noticed by others.t The females are less frequent than the hermaphrodites; their stamens are short, and their anthers, which are of a brighter green whilst young than those of the other form, dehisce properly, ~et contain either no pollen, or a small amount of imperfect grams of variable size. All the flower-heads on a plant belong to *'Die BPfruchtung-,' &c., p. R42. t 1\fr. C. W. Crocker in 'The Gardener's Chronicle,' 1864, p. 294. Mr. W. Marshall writes to me to the same effect from Ely. CHAP. VII. SIZE OF THE COROLLA. 307 the same form. It is well known that this species is strongly proterogynous, and I found that the protruding stigmas of both the hermaphrodite and female flowers were penetrated by pollentubes, whilst their . own anthers were immature and had not escaped out of the bud. Plantago media does not present two forms; but it appears from Asa Gray's description,* that such is the case with four of the North American species. The corolla does not properly expand in the short-stamened form of these plants. Onicus, Serratula, Eriophorum.-In the Compositre, Cnir;u.r; palusfris and acaulis are said by Sir J. E. Smith to exist as hermaphrodites and females, the former being the more frequent. With Serratula tinctoria a regular gradation may be followed from the hermaphrodite to the. female form; in one of the latter plants the stamens were so tall that the anthers embraced the style as in the hermaphrodites, but they contained only a few grains of pollen, and these in an aborted condition; in another female, on the other hand, the anthers were much more reduced in size than is usual. Lastly, Dr. Dickie has shown that with Erioplwrum ang~a;tijolium (Cyperacere) hermaphrodite and female forms exist in Scotland and the Arctic regions, both of which yield seed. t It is a curious fact that in all the foregoing polygamous, dioocious, and gyno-dioocious plants in which any difference has been observed in the size of the corolla in the two or three forms, it is. rather larger in the females, which have their stamens more or less or ~u~te rudimentary, than in the hennaphrodites or males. This holds good with Euonyn1us, Rharnnus cathartic~ts, Ilex, Fragaria, all or at least most of the before-nained Lab~at~, Scabiosa atro-purpurea, and Echium v~tlgare. So It Is, according to Von 1\iohl, with Oarda1nine * 'Manual of ·the B >tany of the N. United States' 2nd edit 1856 f ' • , p. 269. See also 'American Journal of Science,' Nov. 1862, p. 419, ancl 'Pl'oc. American Academy of Science,' Oet. u, 1862, p. 53. t Sir J. E. Smith, ' Trans. Linn. Soc.' vol. xiii. p. 599. Dr. Dickie, 'Journal Linu. So~. But.' vol. ix. 1865, p. 1Gl. X 2 |