GENERAL MORPHOLOGY OF THE PLANT 13 



very small size and very simple structure. In the great group 

 of AlgEe or Seaweeds, in which the gametophyte is the promi- 

 nent form, it is never very greatly developed, though the shoot 

 of the same plant may attain large dimensions. In some of 

 the filamentous floating forms it is often only indicated by a 

 single cell at the end of the filament, and this has only a very 

 short duration. The presence of such a rudimentary root is not 

 considered, indeed, to make the plant more than a thallus. In 

 the sporophyte of the higher cormophytes both root and shoot 

 are well developed and much branched, the shoot being still 

 relatively the greater. 



The shoot usually shows much greater differentiation than 

 the root. Its axis, the stem, gives rise to branches and to 

 leaves. The branches in turn may give origin to other branches, 

 and these to others, thus forming an elaborate branch system. 

 E.ach branch, like the main stem, also produces leaves. The 

 leaves, on the other hand, do not bear appendages like themselves. 



In the higher cormophytes, in which the sporophyte is the 

 prominent form, it produces special shoots for the pui'pose of 

 bearing the reproductive cells or spores. Usually these cells 

 are borne on special leaves, which are then called sjporophylls. 

 Sometimes these sporophylls very closely resemble the ordinary 

 leaves, as in many Ferns ; sometimes they differ from them very 

 markedly in appearance and structure. The special shoot of 

 which they are the leaves is then known as fhe flower, and the 

 branch system constituted by the flowers is called the inflo- 

 rescence. In most cases this is sharply marked off from the 

 general branch system. The flowers have usually, besides the 

 sporophylls proper, certain other external leaves which do not 

 themselves bear spores. 



In the lower plants when the spores have become mature 

 they are detached from the parent plant and germinate indepen- 

 dently, giving rise to a separate gametophyte. In the flowering 

 plants, where the spores are of two sizes, it is only the micro- 

 spores or pollen grains which are so dispersed. The megaspore, 

 or embryo sac, germinates in the sporangium , or ovule, and 

 "ives rise to its peculiar form of gametophyte within itself. 

 By certain appropriate mechanisms the gametophyte arising 

 from the pollen grain is brought into relation with that developed 

 from the embryo sac, and the gametes from the two unite as 

 in other cases to form an oospore. This fusion, which is known 

 as the fertilisation of the oosphere or female gamete, is followed 

 generally by a certain development of the neighbouring parts. 



