255 
But a relative proportion is only less useful than an absolute one 
would be, and if we take 1000 as a convenient approximation to the 
actual total we may compare the state of affairs in 1866 with that in 
1890. In this case we must confine ourselves to introduced phanero¬ 
gams only, and exclude the three cryptogams that have been introduced 
during the interval between 1866 and 1890. The following are the 
I’esults :— 
70 
1866. Pi’oportion of introduced to indigenous species = ^ 
Percentage of introduced species 
=—or.mv. 
146 
1890. Proportion of introduced to indigenous species = or, 1 : 7. 
„ Percentage of introduced species 
= J^or,12-7n„. 
The greater number of these introduced plants are herbaceous ; but 
the proportion of woody species is slowly increasing, as the following 
figures shew :— 
1866. Pi-oportion of woody to herbaceous species = — or, 1 : 37. 
• ^ 
2 
„ Percentage of woody species = — or, 2'63°/o* 
7 
1890. Proportion of woody to herbaceous species = r— or, 1 : 20. 
j.oy 
7 
„ Percentage of woody species = — oi*, 4‘79°/o- 
XtjO 
Human agency is responsible for the introduction of the whole of 
this non-indigenous element in the Flora of the Andamans. That it is 
directly responsible for the introduction of such species as have been 
intentionally introduced that have subsequently become spontaneous is 
self-evident; that it is equally directly responsible for the unintention¬ 
ally introduced weeds is hardly less plain. They are with very few 
exceptions the’ commonest of Indian road-side and rice-field weeds 
whose seeds would readily be found mixed with imported grain or 
attached to the belongings of convict immigrants or of the police sepoys 
of the Settlement. This mode of introduction explains not only the 
occurrence of the weeds of dry ground but of the majority of the marsh 
species, such as Mygrophila, Jussicea, Ludwigia, as well. And species 
of the only class for which this explanation is not altogether satis¬ 
factory— water-plants like Monochoria, Geratopteris, or Ipomcsa aqua- 
tica —nevertheless owe their introduction indirectly to human agency, 
45 
