. A Manual of botany : being an introduction to the study of the structure, physiology, and classification of plants . Botany. EMBRYOGENY IN CELLULAR PLANTS. 267 one cell, considered as the male, pass into the other in which the spore is produced, as in Zygnema (fig. 471), and sometimes the contents of both cells unite, and the spore is produced in the tube between them. Besides this process of conju- gation, by means of which a cellular embryo is formed, some of these plants have a power of merismatic or fissi- parous division (fig. 472), by which cells are separated, capable of inde- pendent
. A Manual of botany : being an introduction to the study of the structure, physiology, and classification of plants . Botany. EMBRYOGENY IN CELLULAR PLANTS. 267 one cell, considered as the male, pass into the other in which the spore is produced, as in Zygnema (fig. 471), and sometimes the contents of both cells unite, and the spore is produced in the tube between them. Besides this process of conju- gation, by means of which a cellular embryo is formed, some of these plants have a power of merismatic or fissi- parous division (fig. 472), by which cells are separated, capable of inde- pendent existence. This may be compared to the process of budding, Kg. 472. and is thus distinct from fecundation. In many of the Confervse, however, spores appear to be produced without the conjugation of separate filaments. In such instances it is conjectured that different cells in the same filament perform different functions, and are so placed that at a certain period their contents by coming into contact develop a fertile germ. The same filament may thus contain both- male and female cells; although botanists as yet have not been able to show the difference between them. In some species of Meloseira the endochrome at each end of the cell appears to have a different property, and mixture takes place in the cavity of a single frustule. In this case there is a movement towards the centre of the cell where the spore is formed. Proceeding to other divisions of Acotyledons, we find different kinds of reproductive organs, which can, however, only be observed at certain periods of development, and frequently cannot be seen after the embryo has been fully formed. In the same way as in flowering plants, when the seed has been ripened the stamens have generally withered and fallen off, and sometimes also the style and stigma. It is of importance, therefore, in all investigations into Cryptogamic reproduction, to examine the plants at an early period of their growth. The reproductive organs
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