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E. sonchifolia, Adenostemma viscosum, Ageratum conyzoides, T riumfetta 
rhomboidea, Urena sinuata, Scoparia dulcis, Abutilon indicum, Sida 
carpinifolia, Commelina nudiflora, Solanum ferox, Hyptis suaveolens, 
H. spicigera, Euphorbia pilulifera, and others. Among the vines are 
Momordica charantia, Merremia hastata, several species of Ipomea and 
others. All are more or less rapidly growing, herbaceous forms with 
seeds adapted to easy distribution. During the dry season many of the 
above have partially disappeared.2* Those which are left show a reduc- 
tion of leaf surface, so that the thinness of the vegetation in these first 
stages is comparable with that of the tree vegetation of the Bambusa- 
Parkia formation. At this time a number of grasses also find a place. 
Among them may be mentioned Panicum pilipes, P. sarmentosum, O plis- 
menus burmannii, and Centotheca lappacea. Imperata exaltata, the 
principal cogon grass, gains an entrance more slowly, but after the first 
year it begins to give a decided aspect to the vegetation. This is due to 
the rapid development of underground shoots by means of which, from 
a common center, it can migrate in all directions, and soon establish a 
more or less dense sod which shades out other forms. With the appear- 
ance of the cogon there is initiated a new period which may be prolonged 
to a greater or less extent. If the soil is shallow, as is often the case on 
an exposed ridge where erosion is great, many of the more mesophytic 
forms, growing with the grass during the wet season, may not be able to 
survive the period of drought, and thus the encroachment of woody forms 
is slow. Nevertheless, if the periphery of the “cogonal” is the edge of a 
wooded area, the shade on the border may be sufficiently dense to make 
impossible the existence of the grass, although woody species which are 
not so light-demanding, may obtain a foothold. With each generation 
the shady periphery advances on the island of grass and in time replaces it. 
Again, in more mesophytic places, a grass land once established offers 
a more or less favorable feeding place for cattle, carabaos, and horses. 
In order that the coarse grass may not become too woody, or for other 
reasons, the owners’may burn the area periodically. Thus many ligneous 
species which may have started are killed, while the geophilous parts 
of the grass are uninjured. Hence, by repeated fires, cogonales are main- 
tained indefinitely and even enlarged at the expense of the neighboring 
woody formation. As soon as the fires are checked, the invasion begins 
anew and in time the grass will be crowded out. The rapidity of the 
invasion of woody species depends on the nature of the surrounding 
* The line between annual and perennial on the one hand and herbaceous and 
woody plants on the other can not be so closely drawn in the Tropics as in 
temperate regions. The life of the same plant may be prolonged in one situation 
over the dry season, while in others, less favorable, it dies down to the ground. 
Most of the plants mentioned in this list can spring from seed, and flower in one 
season. - Usually the rapid growth is during the rainy season while at its close, 
reproductive, activity sets in. Most of those having perennial root stalks become 
more or less woody and persistent and therefore can not strictly be called herbs. 
