SOME CHARACTERISTICS OF VEGETATION OF THE TELL. 1 5 



doubtedly play an important role in the environment of the vegetation of 

 the country At Algiers, in 1907, winds were reported from the north 288 

 times, from the east 203 times, from the west 224 times, and from the 

 south 51 times. At Barika, on the High Plateau, the number of times and 

 the directions of the winds for the same year are as follows: northeast, 

 203 times; east 242 ; south 21, west 89, and southwest 93. At El Golea, on 

 the desert, the winds were as follows: north 192, northeast 614, southeast 

 107. The winds from the north, or northerly winds, are cool and laden 

 with moisture, but they are most effective in regions near the coast or in 

 the mountains. Winds from the south are dry winds, and are probably of 

 great importance in limiting the distribution of plants through the increased 

 aridity caused by them. 



The most important of these desert winds is the sirocco, a wind that 

 is most likely to blow in spring and summer, although occurring in autumn 

 also, and to a very limited degree in the winter season. The sirocco crosses 

 the Mediterranean and is felt in the southern portions of France, on the 

 Italian Riviera, and in other parts of southern Europe. It is especially 

 common on the High Plateau ; for example, during five years it was reported 

 on an average of 28.4 days each year. It does not generally last more 

 than three days, but at Batna, in July, 1902, it was recorded on eight con- 

 secutive days. The sirocco operates to lower the relative humidity and to 

 raise the temperature. For instance, on the first day of the eight-day 

 sirocco above alluded to, the average relative humidity was 16 per cent, 

 while the average on the preceding day was 25.6 per cent. It has already 

 been remarked that on the days of the greatest temperature variation the 

 sirocco was usually blowing. In the desert the winds often bring with them 

 much dust and sometimes last during several days; for example, one is 

 reported at In Salah, in May, 1904, for six consecutive days. Such winds 

 on the desert may come from the north, or at least may be northerly, and 

 when storms of this character are in progress, although possibly destructive 

 of animal life or at least comfort, the effects as regards decreasing the rela- 

 tive humidity and raising the air temperature are not so marked as is the 

 case when the sirocco is blowing. 



SOME CHARACTERISTICS OF THE VEGETATION OF THE TELL. 



Because of the similarity in the flora of Algeria and southern Europe, a 

 very good introduction to Algeria is by the way of southern Spain, France, 

 or Italy. As one approaches southern France, for instance, he begins to 

 see evidences of increasing aridity. Upon passing Lyons grassy fields and 

 heavy forests are left behind, the hills become bare or covered with a 

 chaparral-like growth, and the practice of irrigation is observed on the 

 plains. The vegetation, especially of the region between Avignon and 

 Nimes, recalls that of portions of California, and one sees the mulberry, 

 the olive, and the pomegranate in abundance, and occasionally the orange. 



