44 



ELEMENTS OP BOTANY. 



Perennial plants live for a series of years. Many kinds of 

 trees last for centuries. The Californian giant redwoods, or 

 Sequoias, which, reach a height of over 300 feet under favor- 

 able circumstances, live nearly 2000 years ; and some mon- 

 strous cypress trees found in Mexico 

 were thought by Professor Asa Gray 

 to be from 4000 to 6000 years old. 



67. Stemless Plants. — The so- 

 called stemless plants, like the dande- 

 lion. Fig. 29, and some violets, are 

 not really stemless at all, but send 

 out their leaves and flowers from a 

 very short stem which hardly rises at 

 all above the surface of the ground. 

 Now, as will be shown later (§ 241) 

 plants live subject to a very fierce 

 competition among themselves and 

 exposed to almost constant attacks 

 from animals. 



Any plant which can grow in 

 safety under the very feet of grazing 

 animals will be especially likely to 

 make its way in the world, since 

 there are many places where it can 

 flourish while ordinary plants would 

 be destroyed. The bitter, stemless 

 dandelion, which is almost uneatable 

 for most animals, unless cooked, 

 which lies too near the earth to be fed 

 upon by grazing animals, and which 

 bears being trodden on with impu- 

 nity, is a type of a large class of hardy weeds. 



And while plants with long stems find it to their account 

 to reach up as far as possible into the sunlight, the cinquefoil, 



Fig. 28. — Twigs and Branches 

 of the Iliver Birch. 



