THE FLORA OF MANILA. 
191 
Acrostichum aureum L., Ceratopteris thalictroides Brongn., Val- 
lisneria spiralis L., Ruppia maritima L., Typha angustifolia L., 
Imperata cylindrica Beauv., and doubtless other grasses and 
sedges, Pistia stratiotes L., Lemna paucicostata Hegelm., Spiro- 
dela polyrrhiza SchL, Sesiivium portulacastrum L., Portulaca 
oleracea L., Ceratophyllum demersum L., Cassytha filiformis L., 
Caesalpinia nuga L., C. crista L., Canavalia lineata L., Vigna lu- 
tea A. Gray, Jussiaea suffruticosa L., J. repens L., Hisbiscus 
tiliaceus L., Bacopa moyiniera Wettst., and Ipomoea pes-caprae 
Roth. 
It will be noted that a considerable number of the forms enu- 
merated above are aquatic species or those that grow in swampy 
places, having minute seeds that might readily be transported 
by adhering in mud to the feet or feathers of migratory wading 
or swimming birds. Such plants are Ceratopteris, Acrostichum, 
Lemma, Spirodela, Pistia, Ceratophyllum, Vallisneria, Bacopa, 
Jussiaea, etc., although the wind may have been the agency of 
dispersal in some cases. Others are characteristic species of the 
strand, such as Hisbiscus tiliaceus L., Canavalia lineata DC., 
Cassytha filiformis L., Caesalpinia nuga Ait., C. crista L., Vigna 
lutea A. Gray, and Ipomoea pes-caprae Roth, and are undoubtedly 
ocean-distributed plants. 
While it is comparatively easy to explain the probable methods 
by which species like the above have been distributed, it is, 
excluding the theory of their distribution by man, impossible to 
explain the wide distribution of many grasses and sedges and 
other weedy plants which in most tropical countries are found in 
waste places in and about towns, in fallow lands, and as weeds in 
cultivated fields. While many of these might be distributed by 
winds, by water, or by their comparatively small seeds adhering 
in mud to the feet or feathers of migratory birds, still it is more 
probable that most of them have been disseminated by man, for 
most part inadvertently, in packing material, in earth trans- 
ported for one purpose or another, in ballast, and by other means. 
From the habitats and distribution of such species as the follow- 
ing, it is only reasonable to suppose that most or all of them 
have been distributed by man, although their original homes are 
unknown or uncertain; wherever else they may have originated 
they are certainly not natives of the Philippines: Various grasses 
and sedges, Commelina nud.iflora L., Alternanthera sessilis R. Br., 
Amaranthus spinosus L., A. viridis L., Trianthema portulacas- 
trum L., Mollugo lotoides O. Ktze., M. oppositifolia L., Cissam- 
pelos pareira L.. Cleome viscosa L., Gynandropsis pentaphylla 
