Melocactus Melocactoides HU 237
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VOLUME 13 NUMBER U Melocactus melocactoides HU 237 Actual size < Collection -G . HOLE Full S ize 59 GYMNOCALYCIUM BUENEKERI SETS FRUIT From G. Hole Setting a fruit on G. horstii has been achieved each year now for several years, but only with the help of a brush, usually by using pollen from G. multiflorum or G. hybopleurum. Persuading seed to set on G. buenekeri is a totally different matter however. Since 1980 I have tried to set seed on this plant, but until 1983 I had no luck. It took a lot of work with the brush and also pollen from about 30 different species that happened to be open at the time. I would agree that the stigma lobes on both of these species are longer than is usual on Gymnocalycium - they are about 10-12mm long - but then the flowers are larger too! Flowers on both of these species seem to possess very little pollen. The fruit on G. buenekeri started to swell about two weeks after the flower was pollinated; it then took about ten weeks for the fruit to grow up to the size it had reached when it was on display at the Chileans Autumn Weekend. from J. Lambert Although I have tried to cross pollinate flowers on two different plants of G. horstii, so far I have not obtained any fruit. At first a suggestion of a fruit seems to shape up but then merely withers away. However, I noticed that the flowers of this species were of quite a large size - some 100mm in diameter, 75mm in height and with a pericarpellum of about 20mm. This latter would account for a fruit of nearly 30mm in height. from G. J. Charles This year quite a number of Gymnocalycium have set fruit without any help at all from me. Included in this number is G. buenekeri, which has set a fruit which may be said in general terms to be large for a Gymnocalycium but bears no resemblance whatsoever to the fruit on G. Hole’s plant. from G. J. Swales Towards the end of September the fruit fell off the plant of G. buenekeri which was on loan from G. Hole. It split longitudinally, exposing the seed embedded in a white to colourless pulp. The fruit weighed 113.4gm (about four ounces) when ripe and smelt deliciously of ripe melon and strawberries, although still green in colour externally. All the seeds were separated from the pulp by smearing the mixture onto absorbent tissue and picking out the seed by hand. The seeds were then counted, the final total being 2479. Some twelve of these seeds had already germinated and were growing submerged in the pulp; I transfered these to a closed petri dish containing moist filter paper but unfortunately they all succumbed to a fungal attack. Has anyone been successful in raising seed that has germinated by endogenous vivapary? Although externally the seed looked normal enough, on crushing a random sample, very few indeed contained anything which might have been a viable embryo. If the seed is sown in Spring I would forecast a percentage germination rate in single figures! Although I am never able to get round to hand pollinating my Gymnocalycium flowers, I do obtain an appreciable number of fruits, especially on plants in the G. gibbosum group. As there are very few insects on a roof top four storeys up in the centre of Sunderland, I suspect that quite a number of my fruits must have been set on self-fertile plants, just as G. Charles observes. Equally I would suggest that although G. Hole did apply a great deal of pollen to his G. buenekeri flower, this does not entirely rule out the possibility that it was self-fertile and set it own seed. Where cross-pollination is done by a brush, it is never impossible that a flower could already have set seed by selfing, or as a result of a visit from an insect, before manual intervention. The only certain way of controlling cross-pollination is by emasculation i.e. removal of the stamens before the anthers open to release the pollen. This usually means removal of the stamens just before the flower opens. This is a highly skilled operation which is commonly practised by plant breeders. If done too soon, it may kill the flower, or fail to achieve the intended objective if carried out too late. Immediately the manual cross-pollination has been done, the flower must be enclosed in a porous but insect-proof bag. Unless all this is done, one cannot be certain that the fruit was not set by self-pollination or by the agency of some stray insect. I am very grateful to G. Hole for letting me have this plant on loan since it is the first time that I have been able to study a fruit of this species. from C. A. L. Bercht I have been able to set fruit on G. buenekeri by transfering pollen on to the flower from an Echinofossulocactus. This was the first time that the plant had flowered for me and it set three fruits. These were indeed very large, about 6cm long and 2.5cm diameter. The fruit is still green when ripe and you can see the seeds through the pericarp. The fruit does not split but weakens and I think that in the wild it will break up. The pulp is very wet and thin. Two of the fruits fell off more or less at the same time and I sowed many of the seeds which germinated quite well. I did not count the seeds at the time, but now that you have asked I find that there are about 500 seeds remaining, so I suppose that the two fruits each contained about 350 seeds. Cross-pollination between flowers of G. buenekeri and G. horstii failed to set fruit; perhaps the flowers were not ripe for pollination? Every time I have occasion to look at these two species it amazes me that two so similar looking plants produce such different seed. from H. Middleditch Surely we should not expect seeds to be similar just because plant bodies are similar. A resident of Rio Grande do Sul may well consider as rather similar the overall habit of Beech, Sycamore and Oak in an English wood; it would be unwise to assume that the seed would also be somewhat similar. Speaking of the Tola bushes found on the high Puna, Fiebrig says of Fabiana densa, a Solanaceae, “it is physiognomically in growth, branch formation, leaf form and flower carriage so like the Compositae Tola bushes that only with difficulty can one get accustomed to placing them systematically elsewhere” . Of the cushion plants found on the Puna, Fiebrig mentions a Verbena and also the “white flowering Pycnophyllum pilgerianum which is so similar in habit, leaf form, etc. to the verbena that it can scarcely be distinguished from observation of the surface features” . The admirable illustrations of Opuntia subterraneana and Rebutia pygmaea which appear in Fries’ account of the Puna Flora show two plants of remarkably similar appearance with very different seed forms. The body morphology represents a similar defence response to the hostile macro-environment, whereas the different seeds probably exploit alternative means of survival between plant generations. 60 In a similar way, G. horstii and G. buenekeri both grow in a macroclimate with a very similar temperature and rainfall regime: as far as it is possible to judge from the very limited information that is available, it seems that both plants may well grow in immediate surroundings which are not vastly dissimilar, possibly grassland with sparse bushes. Hence in a similar macroclimate and in similar immediate surroundings, the two species have evolved similar body morphology. On the other hand if the nature of the bedrock and the surface soil derived from the bedrock is considered, it becomes clear that G. horstii grows near Cacapava on soil derived from ancient granitic rocks, whilst G. buenekeri from San Francisco de Assis grows on soil derived from younger sedimentary rock interbanded with deep cills of basalt lava. Gymnocalycium horstii comes from central Rio Grande do Sul where trees are sparse and grow only in more favourable spots, whilst G. buenekeri lies within a zone that originally supported dense and extensive tracts of woodlands. South America supports a vast and varied population of monkeys, of which almost all are tree dwellers. It is possible that monkeys may be found on the southern margins of the Brazilian forests, in Rio Grande do Sul, around the habitat of G. buenekeri. The fruit on G. buenekeri seems to me to be about the size and consistency that might attract a monkey. The environment of G. horstii seems to be unlikely to support any monkeys so it would be a waste of effort for the plant to produce a fruit that attracts a monkey. But I suspect that the different seeds are each in their own way eminently suitable for the quite different surface soils and ground conditions at each location. from Mrs. N. Swales The fruit of G. buenekeri remained green when ripe and possessed a delicious aroma. It could hardly be directed towards bird dispersal, since birds have no sense of smell and are unlikely to be able to see the fruit easily in the surroundings of other green vegetation. On the other hand, many mammals do possess a well-developed sense of smell; so I would suspect that dispersal of the seeds of G. buenekeri would be done by mammals and certainly not by birds.