12 Nebraska Agricultural Exp. Station, Research Bui. 7. 
with the crossed seed, so that, if the parents happened not to be 
homozygous in their more prominent characters, that fact could 
be determined from their progenies. 
All plants, seeds of which have been planted, have been 
grown in an enclosure covered with fine meshed wire netting or 
under individual covers of very thin bunting, mosquito bar, or 
wire netting (Figs. 1-3), except plants grown in the greenhouse 
in midwinter when no bees are present. Individual plant covers 
are not satisfactory where height of plant is to be studied, since 
they can scarcely be made large enough not to interfere with 
Fig. 1. — Enclosure of fine meshed wire netting used to prevent insect pollination. 
normal growth. Moreover, individual wire covers are difficult 
to manage, mosquito bar is too easily torn, and cloth of even 
the very lightest grades increases the temperature under it to 
an injurious degree in this climate. The large wire-netting 
enclosure is therefore now used exclusively. While many insects, 
including species of very small bees, gain entrance to the en- 
closure readily, they apparently do not effect cross-pollination. 
Even when grown in the open garden, beans are not cross-pollin- 
ated so largely as might be expected from the number of large 
bees found visiting the flowers. There is, however, sufficient 
crossing to make results unreliable when the plants from which 
seed is saved for planting are grown in the open. I have observed 
