THE FLORA OF MANILA. 
205 
of anthesis of any species or group of species have only a local 
value. That some species growing in and about Manila flower 
during certain months is no indication that the same species 
will be found in flower in other parts of the Archipelago during 
the same period of time. The dates of flowering for individual 
species are approximately the same only in those regions where 
the dry season and the rainy season cover similar periods. 
Most of our indigenous species have well-defined and restricted 
periods of anthesis, especially the perennial herbs and the woody 
plants, sometimes lasting a few days or a few weeks, more 
rarely extending over several months in a homogeneous area. 
Judging from herbarium records alone it is not infrequent to 
find that certain woody species have been collected in flower in 
all months of the year, taking into consideration the material 
from all parts of the Archipelago. If, however, the material 
is considered by provinces it is almost always found that the 
specimens from one region all flower during a certain period, 
those from another region at another period, etc., more or less 
closely correlated with the distribution of the rainfall. 
Annual species, being more dependent on rainfall than the 
perennial ones, are for the most part found in flower only during 
the rainy season or shortly after its close, and on the whole 
their period of anthesis appears to average somewhat longer 
than for the perennial ones. Very many of the annuals disap- 
pear with the advance of the dry season, only to make their 
appearance as a new generation after the rains have commenced. 
Among the indigenous species the constituents of the strand 
flora and of the mangrove vegetation, including most of the 
perennials and many of the annuals, flower more or less freely 
throughout the year, in this respect being sharply contrasted 
with the inland flora. The explanation of this phenomenon is 
probably to be found in the soil moisture, which in the man- 
groves is practically the same at all seasons, and along sandy 
beaches and tidal streams more or less uniform throughout the 
year. 
An examination of the indigenous and introduced elements in 
relation to their periods of anthesis brings out a striking and 
rather interesting fact. Only about 8 per cent of the indigenous 
species in and about Manila flower all the year, while among 
the introduced ones the corresponding percentage is more than 
70. Very many of the species making up the 8 per cent for 
the indigenous element will be found in the representatives of 
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