14] 



VEGETATIONAL TYPES OF TROPICAL LANDS 



451 



least to damp layers deep down in the ground. Regarding the 

 ' extraordinarily deep-penetrating root systems ' of Tamarisks, it is 

 even reported that they ' could be followed during the building of 

 the Suez Canal in places to a depth of 50 metres ' (transl.).^ Other 

 desert etc. plants, especially among cryptogams, endure drought by 

 drying up almost entirely without harm to themselves. Yet others 

 are densely tufted or compacted, and often in addition closely 



Fig. 155. — -Arizona near-desert scene showing the giant Saguaro (di Sahuaro) 

 Cactus {Carnegiea gigantea) and bushy Ocotillo (Fouquiera splemleiis). (Phot. 



F. Shreve.) 



invested with hairs and spines, while many, such as Cacti and cactus- 

 like Euphorbias, store water in their massive stems or other swollen 

 organs. Usually these ' succulents ' have an extensive system of 

 roots spread out near the surface of the soil and ready to absorb 

 considerable quantities of water when it comes, for most deserts have 

 a short rainy season during which conditions are fairly favourable 

 for plant growth — especially with the aid of the rich nocturnal dew 

 which may occur. At such times annuals spring up and quickly pass 

 through their whole cycle of development,' while geophytes, with 



^ K. Rubner, Neudammer forstUches Lehrbuch (Neumann, BerUn, i Lieferung, 

 p. 180, 1948). 



^ After the heavy rains in central Iraq in the spring of 1957, the author observed 

 small Plantains {Plantago spp.) and Grasses (especially of the genus Schismus) and 



