528 PART Iir — THE CLASSIFICATION OF PLANTS. 



Ill Casuar'na the pollen-tube does not enter the ovary by the style, but makes 

 its way through the tissue of the wall of the cviry into the placenta, whence it 

 penetrates into the ovule by the chalaza : the pollen-tube now grows towards 

 the micropylar end of the ovule through one of the elongated sterile macro- 

 spores (see p. 438), and comes into close relation with the fertile macrospore, 

 without, however, entering it ; the male cell is apparently extruded from the 

 pollen-tube into the macrospore, and enters the oosphere from below. The ter- 

 minal portion of the pollen-tube becomes, in this case, completely abstricted off 

 from the rest : and generally, when the pollen-tube is very long, the terminal 

 portion becomes shut off from the rest by a plug of cellulose. Some other 

 Atnentales (Corylus, Carpinus, Alnus, Betula) also are chalazogamic. 



The Results of Fertilisation. The Seed is described on p. 458. 



The Fruit. In view of the variety in the structure and morph- 

 ology of the fruit of Angiosperms, a somewhat detailed account of 

 it is necessary. 



The yford fruit, in its strictest sense, means the whole product 

 of the development of the gynseceum as a result of fertilisation. If 

 other parts of the flower take part in the formation of the organ 

 which is formed in consequence of fertilisation, and which contains 

 the seed (of what, in short, is commonly called the fruit), it is 

 termed a spurious fruit or pseudocarp. The apple, for instance, is 

 such a spurious fruit, for the outer fleshy part belongs to that 

 part of the axis of the perigynous flower which surrounds the 

 ovaries and which still bears the sepals (Fig. 2 A). What are 

 called the pips of the apple are the seeds. This kind of spurious 

 fruit is termed a pome. The strawberry also is a spurious fruit: 

 in it the receptacle, which belongs of course to the axis, de- 

 velopes largely and becomes fleshy and bears the true fruits 

 (achenes) in the form of small hard grains. The fig is another 

 example of a spurious fruit ; it is in fact a fleshy receptacle 

 {i.e. an axis) which bears a multitude of distinct flowers situated 

 inside the cavity of the receptacle, and the individual fruits 

 appear as hard grains ; such a fruit is termed a syconus. Again, 

 when the ovaries and floral envelopes of closely crowded flowers, 

 as in the Mulberry and the Pine-apple, become succulent, a kind 

 of spurious fruit is formed which is termed a sorosis. 



In other cases, a husk, called the cupule is formed, which contri- 

 butes to the formation of a spurious fruit : this is formed by the 

 bracteoles and is not developed until after fertilisation ; it may 

 surround either a solitary distinct fruit, like the acorn-cup, or 

 several distinct fruits, like the four-valved spiky husk of the 

 Beech-tree or the prickly husk of the edible Chestnut. 



