1953] 



VEGETATION OF NY AS ALAND 



169 



side. Travelers using regular routes, and people who burn as a personal safety 

 measure, do their firing as soon as the grass will bum. 



Much burning in connection with land clearing is done well on in the dry 

 season, when the ground is broken in preparation for planting after the rains 

 begin. It is then, when soil and ground cover are very dry, that there is most 

 danger of the fire getting away, and if it does leave the clearing and spread 

 to woodland or grassland, the chances are that no very strenuous effort will be 

 made to stop it. Late-season fires of such origin, or those started by irresponsible 

 travelers or the inevitable * 'fire-bug,*' often spread over large areas of country. 

 Often, too, they will be stopped at the edges of areas burned over earlier in the 

 season, or be checked on unburned territory that has been heavily grazed and 

 trampled by domestic animals, and go out when the wind dies down in the eve- 

 ning. But in any inhabited area of woodland or grassland in which fire control is 

 not rigidly enforced, or the grass is not kept down by very heavy grazing, most of 

 the country will be burned over at some time during the dry season and grass 

 which escapes fire one year will almost surely go up in smoke during the next year. 



Speculation as to the effects upon vegetation of fires lit by man have been 

 carried far, with, it seems, too little appreciation of the fact that far reaching 

 fires often are started by lightning in semiarid regions, and that fire therefore 

 should rightly be regarded as a natural factor of the environment in such regions. 



In country uninhabited and unvisited by man there are no checks to the spread 

 of fire other than natural features such as streams and open bodies of water, 

 marshes and swamps, tracts of non-inflammable vegetation, and barren ground of 

 one kind and another. Under conditions of this kind, fires started by lightning are 

 likely to travel farther and perhaps do more damage to vegetation than in in- 

 habited regions where early burning is practiced and other types of firebreaks are 

 produced. 



Grass-fires started by lightning may occur at any time during the dry season. 

 Ephemeral "fire- grasses" will burn soon after the rains, but they are usually re- 

 stricted to habitats of small area unfavorable for the prevailing perennial grasses. 

 It is not until the dry season is well advanced that, in a normal year, the main 

 body of grasses is so dried out that it is in condition to carry a fire that will burn 

 day and night and sweep over large areas of territory. And this is the time when 

 lightning is most frequent; the time of the dry storms with severe lightning, crack- 

 ling thunder, wind, but often not a drop of rain to moisten the grass and so pre- 

 vent the spread of any fire that is started during the disturbance. Fires started in 

 this way will sometimes burn for weeks, until doused by rains from other thunder- 

 storms or the first rains of the wet season proper. Such fires, undoubtedly started 

 by lightning during dry thunderstorms, are to my personal knowledge common in 

 northern parts of Australia, under conditions of climate, and woodland or open 

 forest vegetation, comparable to those prevailing over much of Nyasaland and 

 tropical Africa. 



Fires t started by lightning will not occur as frequently as fires lit by man, but 

 in areas where they are the only fires, and the country escapes burning for a time, 

 the fires when they do occur will be all the more intense and harmful to vegeta- 

 tion owing to the accumulation of dead and dry material from more than one, and 

 perhaps several, seasons of growth. 



PREVIOUS BOTANICAL COLLECTIONS 



The first collections of plants to come out of the area now called Nyasaland 

 were from the Livingstone expedition of 1859 and a second expedition led by 



