Ovule and seed development of Lacandonia schismatica (Lacandoniaceae).

Ovule and seed development is described for Lacandonia schismatica, a species whose androecium is surrounded by the gynoecium. The ovule in each carpel is basal, anatropous, tenuinucellate, and bitegmic. The female gametophyte is formed by the micropylar megaspore cell, after a coenocytic stage of the four megaspore nuclei. The mature female gametophyte has the normal complement of seven cells and eight nuclei. We propose a new type of female gametophyte development on the basis of the coenocytic stage of the tetrad, the cellularization of the tetrad, and the survival of the micropylar spore. At seed dispersal time, the embryo has ~10-20 cells. Endosperm development is of the nuclear type. At maturity, endosperm cells show starch and protein inclusions as well as polysaccharides in their thick walls. The seed coat is formed from the outer integument; the inner one disappears. The exotesta contains tannin. The fruit (achene) wall is two-layered. The maturation of the fruits in a flower is synchronous, and they separate from the receptacle for dispersal.

[Experimental study of post-labyrinthectomy compensation by means of the torsion pendulum]. / Estudio experimental de la compensación post- laberintectomía mediante el péndulo de torsión

Recovery patterns after unilateral labyrinthectomy were studied using a torsion pendulum to produce angular accelerations in unanaesthetized, immovilized cats. The oculomotor activity before and during angular accelerations was recorded and cuantified in 10 post-labyrinthectomized cats during 26 days of recovery both with and without environmental fixation (eyes open or covered). The integrated nistagmus obtained with rotation in each direction was used as a measure of oculomotor activity, as well as an indicator of directional preponderance. It was found this indicator to be far more sensitive than the raw electronystagmic tracings to detect asymmetries in the oculomotor response. The integrated movement of the eyes without ambiental fixation (eyes covered) was consistently 40% of the pendulum's displacement; while having both eyes open, the ocular displacement was equal (100%) to that of the environment. These relations changed in a predictable and characteristic way after labyrinthectomy. Approximately between 5 and 12 days post-labyrinthectomy, the responses to stimulus in both directions become of very small magnitude, indicating a depression of the reflexes originating in the remaining normal labyrinth.