98 BOTANICAL GAZETTE [FEBRUARY 
though not always. When development takes place, the tapetum 
is also found to be normally developed and functional. In some cases, 
as in figs. 43 and 44, the normal number of four nuclei is found (three 
shown in the figures), though these may vary in size (fig. 43) and in 
chromatin content. In other cases (fig. 45) chromatic bodies are 
found in the cytoplasm. In jig. 46 one of the nuclei has two others 
lying near it. Fig. 47 shows a tetrad with extra nuclei. Occasionally 
large and irregular shaped nuclei are found, as in fig. 51. Fig. 48 
is a section of a tetrad showing an extra nucleus formed from a single 
chromosome and connected by spindle fibers with one of the larger 
nuclei. Fig. 49 is a portion of a tetrad showing a nucleus with a 
smaller one beside it; and fig. 50 similarly shows two small extra 
nuclei, each containing two chromosomes. Pairing of the chromo- 
somes in the large nuclei of the tetrad is sometimes seen. Chromo- 
somes are frequently found just outside the nuclear wall; this is 
probably due to tardiness in passing to the poles of the spindle. Such 
chromosomes may or may not be surrounded by a “‘nuclear mem- 
brane.” Most of the pollen tetrads show evidences of breaking down, 
and a great many are more or less completely degenerated. In the 
O. Lamarckiana hybrid irregular-shaped pollen grains are quite 
common in some anthers; jig. 52 shows some of these irregularities. 
There may be extra lobes or fewer lobes than the normal, and they 
may be irregularly placed. Occasionally complete sterility of certain 
anthers of a flower may be found in the O. Lamarckiana hybrid, as in 
O. lata. 
Discussion 
A full discussion of the literature bearing on the facts set forth 
in this paper will not be attempted at this time, as the work touches 
upon several distinct fields. But I shall mention a few of the most 
important papers bearing directly upon these investigations, and 
close with a short discussion of the general bearing of the most impor- 
tant results. 
THE EXTRA NUCLEI IN POLLEN TETRADS 
Witte published a paper (34) on pollen development in the 
angiosperms in 1886, before botany had acquired its present tech- 
nique, in which he cites a list of cases of extra nuclei in the tetra 
