230 THE USE OF THE MICROSCOPE 



clirom-acetic-formalin. Uvularia, Hyacinthus, Datura, 

 Pelargonium, or Oenothera seem worthy of trial. Wash in 

 graded alcohols. Cut in paraffin. Wash sections in 70 

 per cent alcohol for a day or more. Stain with iron- 

 brazilin, iron-hsematoxylin in 70 per cent alcohol, or with 

 iodine gentian violet. (Welsford, Sax, etc.) 



33. Polyembryony of Citrus. — Polhnate an orange flower 

 heavily. In due time, cut longitudinal sections in paraffin 

 of the young ovules. Fix in chrom-acetic-formahn, after 

 opening the ovary, or the larger ovules. Omit washing 

 with water. Wash sections well in 70 per cent alcohol. 

 Stain with iron-brazilin, or iron-hsematoxylin in 70 per 

 cent alcohol, or try iodine gentian violet. Contrast the 

 adventitious embryos with the embryo close to the micro- 

 pyle resulting from the pollination. (Strasburger, Osawa, 

 Belling, etc.) 



34. Pollination of Mangifera indica. — Fix in chrom- 

 acetic-formalin and cut sections in paraffin of mango 

 flowers at, and soon after, pollination. Wash in alcohol. 

 Stain with iodine gentian-violet, or with alcoholic iron- 

 hsematoxylin, or with iron-brazilin. Use the varieties 

 No. Eleven and Cambodia, which have adventitious 

 embryos ; and also some of the varieties which have only one 

 embryo. Does the pollen tube reach the egg cell in the 

 former? (Belling.) 



35. Pollen Tubes of Semisterile Species Hybrid. — Cross 

 the Georgia velvet bean, Stizolohiuin {Mucuna) deeringia- 

 num, with the Yokohama bean, S. hassjoo. (They can be 

 raised to flower in a greenhouse.) From the resulting 

 first-generation hybrids remove the ovaries at the proper 

 time after pollination, cut them open at both ends, and put 

 them in chrom-acetic-formalin, using the air pump if 

 necessary. Omit washing. Cut in paraffin to longitudinal 

 median sections. Wash in 70 per cent alcohol. Stain with 

 brazilin, iron-haematoxylin in 70 per cent alcohol, or iodine 

 gentian-violet. Half the embryo sacs cease developing 

 early. Note that no pollen tubes pass to ovules having 

 such aborted embryo sacs. (Belling.) 



