Card Mounts for Root-Tips in the Paraffin Method.
L. F. Randolph
To facilitate the handling of root-tips in the paraffin method they may be mounted on cards in the following manner.
- Prepare small pieces of heavy paper approximately 2 cm. x 2.5 cm. in size (the heaviest grade of Y and E filing cards is suitable). Smear the base of a card with DuPont household cement, or Lepage's waterproofing cement. Add roots and cover with more cement, leaving at least .5 cm. of the tip of the root free (fig. 1). Invert at once in the fixing fluid, keeping the cards separated until the cement has partially hardened.
- After fixation and transfer to 75% alcohol, snip off the tips of the roots from the original card in a petri dish containing a small amount of alcohol. Prepare a second smaller card, approximately 7 x 12 mm. in size. Label one side (Fig. 2a), and coat the other side with a thin layer of mucilage, using a clear, amber-colored grade of Carter's or Stafford's mucilage evaporated to the consistency of heavy syrup. Rapidly transfer the roots one by one from the petri dish to blotting paper for removal of the excess alcohol, and then to the second card. Add more mucilage and a thin strip of paper to help hold the roots in place (Fig. 2b). Immerse the card with roots attached at once, right side up, in 85% alcohol. The mucilage may be conveniently applied with a No. 2 or No. 3 camel-hair brush. For transferring the roots quickly from the blotting paper to the card a bent dissecting needle applied to the moist surface of the root is very effective (Fig. 3). The final orientation of the roots on the card may be completed after transfer to 85% alcohol. The root-tips should project approximately 2 mm. beyond the edge of the card, and care must be taken that the tips are kept free of mucilage since it causes trouble in sectioning.
- After the mucilage has hardened the card mounts are placed in a 30 cc. or 50 cc. pyrex beaker and dehydration and infiltration are completed in the usual manner. The mounts should be embedded with the labelled side down so that the mounts may be identified readily. Paraffin ribbons from two or more card mounts may be placed on the same slide (Fig. 4).