372 
POPULAR SCIEKCE BETIEW. 
the other — if not to make the machine, at least to set it 
going, and regulate its action according to his wishes. 
In this place we may appropriately call attention to the 
opinions of Mr. Meehan on the sexuality of plants, and which 
demand attention as the opinions of a practised cultivator, a 
good observer, and a shrewd reasoner.* As the result of his 
observations, he comes to the conclusion that in plants a high 
degree of vigour produces the female sex, while a less robust 
constitution is sufficient for the development of the pollen. 
In this manner the alternation sometimes observed in unisexual 
plants may be accounted for. A plant producing fruit, and 
more particularly ripe seed, for a succession of years, becomes 
more or less exhausted, and during the period when it is 
recruiting its energies it forms male flowers only. Mr. Meehan 
bases his theory on the relative position of the flowers of the 
two sexes, showing that the female flowers are, as a rule, placed 
on the strongest axial parts, the male ones on the weakest. As 
a consequence of this, the female flowers are so placed as to 
receive the direct flow of the nutrient fluid, while the male 
flowers often derive their supplies from collateral, or less direct 
sources, and in smaller quantities. He further goes on to show 
that the invigorating effects of climate, of manuring, &c., tend 
more particularly to the development of the female rather than 
to that of the male flower. 
Apart from ascertained facts, it seems reasonable to suppose 
that a less degree of vital energy would be required for the 
staminate flowers, whose functions are much sooner fulfilled, 
than for the pistillate flowers, whose oflSce of forming, pro- 
tecting, ripening the pistil, and more especially its contents 
(the ripe seed), naturally occupies so much longer a period, and 
involves so much larger a demand on the resources of the plant. 
There are several facts which lend colour to this theory. In 
America, strawberry-blossoms are frequently unisexual. In this 
country, also, some varieties are apt to produce “ blind,” i.e. 
sterile flowers. The same thing happens in vines, and indeed 
in many other plants. Spruce and Meehan, as we have seen, 
would consider this tendency to produce unisexual flowers as 
an evidence of progress ; and so indeed it may be, on the prin- 
ciple of division of labour. The gardener, however, looks upon 
the occurrence in quite a different light, and does his best to 
rid himself of such undesirable plants. But if the advantage 
accruing from division of labour, and specially from the opera- 
tion of cross fertilisation, were fully recognised by him, he should 
rather promote than discourage such a tendency, and counteract 
the sterility by the artificial employment of pollen from some 
Cited in Gardener’s Chronicle,” 1870, p. 243. 
