2. Who put the first bags on corn plants?
In his experiments on the effects of cross and self-fertilization Darwin covered his plants with cotton netting, but I can not find any statement that he used bags of any kind. His corn plants were isolated by putting single plants without covering in different parts of a greenhouse and allowing pollination to take place naturally. The cross‑pollinations with all of his plants was brought about by natural means.
In the Michigan Board of Agriculture Report for 1881, W. J. Beal states that paper sacks were put on corn plants for the purpose of making cross pollinations.
According to P. G. Holden, Beal and his assistants about 1885, in their experiments at Michigan Agricultural Experiment Station, used both paper and cloth bags. The cloth bags were dipped in oil, thinned with turpentine and dried before using to make them waterproof. To eliminate the inconvenience, or risk, in removing the sacks from the tassels and ear shoots they inserted a blow gun into the tassel bag to suck up the pollen and then into the sack over the ear shoot to blow the pollen on to the silks.
McCluer, in his experiments with corn at the Illinois Experiment Station, published in 1892, used cloth bags. Pollen was gathered on a sheet of smooth paper and this was rolled into a funnel to facilitate the application of the pollen to the silks. When the pollinations were made an umbrella was held over the ear shoots to protect them from drifting pollen. Morrow and Gardner at the same Station, in a report one year later, put cloth bags on the ears and paper bags on the tassels. Collins and Kempton in 1912 tried paper tubes extending from the tassel to the ear on the same plants. Roberts at the Kansas Station used this same type of tube to make crosses between plants growing in adjacent rows. Jenkins devised the bottle method in 1922. Excised tassels were kept in a functioning condition by inserting the stems in water in a bottle wired to the stalk below the ear. This method is now extensively employed in the drier sections.
Paper bags on both tassels and ears were tied with string at first. Roberts at the Kansas Station in 1911 fastened paper bags on the ears and tassels with large pins. Coiled wires have been used by Collins and Kempton to permit expansion of the ear shoots. Paper clips were first tried about 1922. Later, wire stapling clippers have been used extensively.
Roberts resorted to an insect powder blow gun to apply pollen in 1911. Merle Coulter in 1919 devised a glass thistle tube blow gun that could be easily sterilized in alcohol.
Small glassine bags to cover the ear shoots replaced the larger manila bags in 1922, or before.
Early corn pollinators worked in pairs and went to a great deal of trouble to sterilize their hands in alcohol before each pollination. When it was found that most of the contamination comes from insects traveling up the stalks and from pollen drifting in the air, these elaborate precautions were discontinued. Pollination was further simplified by cutting back the silks to a short stub, At the Connecticut Station a knife sterilized in alcohol was used at first. Later it was found that a sterile knife was not necessary if the shoot was cut back below the tip of the ear shoot.
Much of the insect and wind contamination can be avoided by using an ear bag small enough to fit tightly around the ear shoot, or by folding one of the lower corners and tucking this in between the ear shoot and the stalk. Pollen is applied after tearing off the top of the glassine bag without removing it. The bag is folded over afterwards. The tassel bag, or a similar one, is placed over the ear shoot bag after pollination and fastened with a paper clip or wire staple.
D. F. Jones