Comparing proportions between groups

Hello there,

I have two groups (men and women) and I know per group how many of them
smoke or don't smoke (women 40 of 200; men 100 of 300). I would like to know
how I can compare in R if men and women differ significantly in their
smoking.  However, because there are more men in the sample than women I
cannot just compare the number of smokers and non-smokers in both groups,
right?! (I would not really know how to do that either, to be honest :(). 

I have done this:

gensmoke <- table(data$gender,data$smoke)   	#save table 

old.digits = options("digits")        # store the number of digits
options(digits=3)                     # only print 3 decimal places
gensmokePROP = prop.table(gensmoke,1)    #table of the proportions I'd like
to compare

                smoker  non-smoker
women       0.200   0.800
men          0.333   0.667


But then when I try to run a t-test on it, for example

t.test(gensmokePROP[3], gensmokePROP[4], alternative = "less")

then R tells me that there are not enough observations in x.
Could anyone help me? That would be really great. Thank you,
Lila