162 SYSTEMATIC BOTANY. 



developed. The fibro-vascular bundles are either closed, 

 or open, and consist of all kinds of tissue, except collen- 

 chyma. The fundamental tissue is mostly parenchyma ; but 

 in the hypodermal portions it may contain collenchyiria 

 and sclerenchyma. In certain orders laticiferous tissue 

 is also common. But few of the plants are parasitic or 

 saprophytic ; they are mostly chlorophyll-bearing. They 

 vary in size from excessively small to excessively large 

 plants, and in duration from a few days or weeks to 

 hundreds of years. They are divided into two classes, 

 Gymno^ermce and AngiospermoB. 



GYMNOSPERM^. 



183. The Gymnospermous plants, which include the 

 Cycads, Pines, Firs, etc., have naked ovules, that is, not 

 enclosed in an ovary ; and the endosperm arises in the 

 embryo-sac before fertilization takes place. They are all 

 terrestrial, chlorophyll-bearing, and, with few exceptions, 

 large trees. The flowers are always diclinous, that is, the 

 staminate and pistillate organs are in different flowers. The 

 pollen is transported by the wind (hence, the immense 

 quantity produced) from the anthers to the ovules, whose 

 orifice (micropyle) is at this time filled with a fluid. This 

 drying carries the pollen grains down till they come in 

 contact with the nucleus, or body of the ovule, when they 

 germinate and produce pollen-tubes, which pierce the soft 

 tissue, and reach the elongated bodies, called the corpus- 

 cula (which seem to be homologous with the archegonia 

 of previous divisions), which arg developed in the embryo- 

 sac ; and the result of this contact is fertilization and 

 consequent formation of the embryo-sac. This takes place 

 as follows: The lower, or germ-cell of the corpusculum, 



