Sentence Examples with the word welwitschia

The megaspore of Welwitschia is filled with a prothallus-tissue before fertilization, and some of the prothallus-cells function as egg-cells; these grow upwards as long tubes into the apical region of the nucellus, where they come into contact with the pollen-tubes.

It remains to be seen if the ovuliferous cone in the centre of the flower represents simply a functionless gynoecium, as in Welwitschia and abnormal cones of certain Coniferae, or if the flowers were hermaphrodite, with both male and female organs fully developed.

In certain species of Gnetum described by Karsten the megaspore contains a peripheral layer of protoplasm, in which scattered nuclei represent the female reproductive cells; in Gnetum Gnemon a similar state of things exists in the upper half of the megaspore, while the lower half agrees with the megaspore of Welwitschia in being full of prothallus-tissue, which serves merely as a reservoir of food.

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In Welwitschia also the megaspore is filled with prothallus-tissue, but single egg-cells take the place of archegonia.

In the Gnetaceous Welwitschia it possesses a vegetable type whose extraordinary peculiarities make it seem amongst contemporary vegetation much as some strange and extinct animal form would if suddenly endowed with life.