With a view of increasing the present knowledge of the minute structure of the twigs, including buds, of various varieties of apple trees the investigations herein described were prosecuted during the months of December (1888), and January (1889). The twigs were either taken directly from trees growing near the College or from a cellar where they had been stored in late autumn. In some cases samples were ordered from other parts of the state and examined upon their arrival. Primarily the investigations were carried out to determine the conditions in which the various food-materials, formed by the trees were stored up for future use; and in the second place to find if there was any marked differences in the amounts and qualities of these reserve food substances or any other constant differences among the varieties subjected to microscopic examination.
Halsted, Byron D.
"An investigation of apple twigs,"
Bulletin: Vol. 1
, Article 4.
Available at: https://lib.dr.iastate.edu/bulletin/vol1/iss4/4