Classification of Plants 



295 



axile or nearly basal but by rapid growth of the tissue the 

 seeds are carried out so that the placentation becomes parietal. 



In this order are to be found some of the interesting types, 

 first described by Dr. Marloth, of plants with " window leaves " 

 which lie covered with earth except the upper end which is 

 more or less flattened and transparent. Through this region 

 the light penetrates to the underground part where the chloro- 

 phyll is formed. In the clear central cells of the leaves the 

 light comes to a focus and is then diffused to the chlorophyll 

 at the margin. When the sand washes off so as to expose the 

 leaves above ground they become quite red, which serves to 

 protect the exposed chlorophyll from the heat rays (see p. 

 116). 



Tetragonia. — Calyx 4-parted, yellow within. Stamens 

 varying in number. Ovary inferior, 1-9- celled (usually 4- 

 celled). Fruit sharply 4-angled, winged or horned; cells i- 

 seeded. Succulent herbs, spreading, or sometimes erect and 

 shrubby. Fruit often ripening under the protection of the 

 fleshy leaves close to the ground. 



Order Caryophyllace^. 



Flowers with both calyx and corolla or carolla wanting. 

 Stamens 4-10, free from the perianth, obdiplostemonous. 

 Ovary superior, i -celled, or at the 

 base 2-5-celled. Styles 2-5. Ovules 

 2 -many. 



Placentation is usually known as 

 '* free central " but it seems to be 

 axile with the adjacent walls of the 

 carpels broken down. Traces of the 

 septa may be seen at the base of the 

 ovary. Fruit usually a capsule de- 

 hiscing by apical teeth. 



The inflorescence is definite form- 

 ing a dischasial cyme, but often one branch outgrows the other 

 and at length one branch does not develop at all so that a 

 cincinnus appears. In some a cincinnus appears from the 

 start. 



Fig. 



267. — Floral diagram 

 Silene venora. 



