A HUNDRED MICROSCOPICAL OBJECTS 219 



2. Segments of Chromosomes Comiected by Threads in 

 Pollen Grains of Uvularia. — Plants of Uvularia wintered 

 outside are to be put in a warm greenhouse in February. 

 Flowering shoots are to be examined as soon as they appear 

 above ground. Pollen grains at the right stage were fixed 

 and stained by the writer in iron-acetocarmine ; but they 

 might doubtless be smeared, fixed in chrom-acetic-formalin, 

 and stained with, iron-brazilin, or iodine gentian violet. 

 Chromosomes VI and VII show a fiber between their seg- 

 ments, sometimes as long as the longer segment. By local 

 pressure, the cells in acetocarmine can be flattened and 

 some of the cytoplasm pressed out, so that the chromosomes 

 show more clearly. (S. Nawaschin, Belling.) 



3. First Anaphase of Chromosomes in Pollen Mother 

 Cells of Haploid Plants. — Haploids can sometimes be 

 obtained by exposing plants to alternations of cold and heat, 

 or by crossing with pollen of related species which rarely 

 fertilizes the ovules. An anther can be tested from each 

 bud until the right stage is found, the contents being pressed 

 out in iron-acetocarmine. Smears may be fixed for 2 

 to 5 hours in chrom-acetic-formalin, mordanted in iron alum 

 for 24 hours, stained from 2 to 12 hours in brazilin, or 

 alcoholic haematoxylin, differentiated in iron alum, and 

 mounted in immersion oil, with covers 0.17 millimeter thick. 

 Cells showing the desired stages are to be flattened by 

 pressure on the cover with the point of a thin-bladed pen- 

 knife. If any of the chromosomes can be identified by size 

 or shape, the question is if the assortment at first anaphase 

 is a purely random one. (See, for Datura, Belling and 

 Blakeslee; for Nicotiana, Clausen and Goodspeed; for 

 Triticum, Gaines and Aase; and for Crepis, Hollingshead.) 



4. Ultimate Chromomeres of Lilium, Aloe, and Fritil- 

 laria.— Plants of Lilium pardalinum are grown to flower 

 in a shady place. Buds of various lengths under 20 

 millimeters have one anther removed, to be tested in 

 iron-acetocarmine. At the pachytene stage, the remaining 

 anthers are removed, split lengthwise, dried with filter 

 paper, cut across once, put across the slide en echelon, and 



