26 . BOTANICAL GAZETTE [JANUARY 
situation and far greater probability of frequently finding sufficient 
moisture for the swimming sperms. In fact, neither of these lyco- 
pod seeds shows any signs whatever that pollen ever lodged on 
the nucellus. Miadesmia actually possesses integumentary out- 
growths that appear to be designed to prevent pollen from entering 
the micropyle. Though these hairs would probably keep pollen 
from entering the micropyle, they would serve equally well to 
catch it and retain it near the ovule. Sperms freed here would 
be in a favorable position to reach the archegonia with a minimum 
amount of moisture, which might very well be exuded by the 
cone scales, just as it is today in Araucaria. The reasons for the 
formation of pollen tubes in this type of pollination are no greater 
than in the previous type, but once formed and endowed with the 
habit of growth toward the archegonia, they would add immensely 
to the probability of fertilization, and so would tend to be selected 
and preserved in the evolution of the seed. Such tubes would 
probably always have grown toward the micropyle of the ovule 
because of the greater opportunity of securing suitable food in that 
direction. They would probably branch for the same reason that 
fungus hyphae branch (whatever that reason may be). Probably 
the main branch did not at first regularly reach the nucellus, but 
only came to do so later, after the nucellus had acquired the habit 
of secreting some chemotropically active substance. Then if the 
pollen tubes in search of food ever came to penetrate the nucellus 
before it had been broken through by the female gametophyte, 
they would furnish a more direct and easy route for the swimming 
sperms to the archegonia than for them to be freed outside the 
ovule as in the earlier stage. An advantageous habit of this sort 
would be likely to be preserved. We thus attain the state of © 
affairs illustrated by the araucarians. 
It is perhaps worth while pointing out that, in the above argu- 
ment, the various changes are not supposed to have occurred because 
they would be advantageous, but having occurred fortuitously to have 
been preserved because they were advantageous. In contrast, the 
theory outlined above (11) of the derivation of pollen tubes among — 
the conifers and araucarians requires the derivation of disadvanta- 
geous changes and their selection and preservation notwithstanding. 
