SECTIONAL TRANSACTIONS.—M. 463 
The sterility of potato flowers, particularly on the male side, is a well-known 
fact, and a knowledge of the condition of the anthers is required at the outset 
of any hybridising work in order to avoid unnecessary labour and waste of 
time. 
As the results of Tackholm and others show, such an investigation should 
lead to a better understanding of some phylogenetic and systematic problems. 
The five anthers of the potato are long and fleshy. The yellow colour is 
due to a pigment in the anther wall, the pollen itself appearing as a white 
powder to the naked eye. 
In the economic varieties of potato two distinct types of pollen have been 
identified—long and short. The long type is found in the anthers of Myatt’s 
Ashleaf and in some hybrids derived from this variety, whereas in Great Scot, 
Leinster Wonder, Majestic, Ker’s Pick, and in many others, the pollen grain 
is polygonal in shape, being about as long as it is broad, with usually a 
pentagonal face at each end. Amongst this latter type of grain are a consider- 
able number of giant or compound grains. These giants appear to be perfectly 
healthy, and in rapidly degenerating pollen, such as is found in Great Scot, are 
the last to survive. 
L'ypes of Pollen Degeneracy.—Three types of anther degeneracy have been 
demonstrated in the varieties of potato grown at the present time. 
1. The anthers of many economic varieties contain a larger or smaller per- 
centage of shrivelled grains. In Great Scot, for example, most of the grains 
are found to be shrivelled and empty. The degeneration of the grain takes 
place after the formation of the pollen mother cell. 
It must be supposed that the breakdown occurs immediately after the release 
of the grain from the pollen mother cell. The nucleus is first observed to 
degenerate, the cytoplasm becomes thin, and takes stains with difficulty. 
Finally the contents of the grain entirely disappear, leaving only the empty 
skin. This type of pollen degeneracy is by no means uncommon among 
angiosperms, and it is of interest to note that the breakdown rarely occurs 
previous to the formation of tetrads. This has been found to be the case by 
Juel in Syringa chinensis, Geerts in Wnothera Lamarckiana, and Dorsey in 
the Grape. I have also found the same stages of degeneration in Petunia and 
Rosa hybrids. 
2. Hypertrophied Grains.—A form of degeneration in potato pollen which 
occurs frequently in the same anthers as does the shrivelled pollen type of 
degeneration just described is that of hypertrophied or swollen grains, many of 
which contain minute bodies which give the starch reaction when treated with 
iodine. In all examples of potatoes producing pollen I have found a smaller 
or larger percentage of these hypertrophied and starch-filled grains. When 
placed on the stigma some of them have been observed to send out germ tubes, 
which are distinguished from the pollen tube of the normal grain by their 
inflated and irregular shape. Similar hypertrophies have been found by me in 
Petunia and Rosa hybrids. They have also been described for Rumex crispus 
by Winfield Dudgeon (Bot. Gaz., Nov. 1918). 
3. Up-to-date l'ype of Pollen Degeneracy.—Several varieties of potato 
exhibit the form of anther degeneracy to be described below. The usual case 
for this type is for no pollen to be formed at all. Section of very young anthers 
of Up-to-date flowers show pollen mother cells which are apparently normal. 
No reduction division has been observed. Slightly older buds, in which the 
anthers are still quite green, have the anther sacs filled with bodies, many of 
which have the appearance of hypertrophied mother cells. These bodies vary 
in size and shape and granular density. Some consist of a network of cells, 
each cell of which is more or less pentagonal, and some of which were observed 
to have five round chromosome-like particles of chromatin. Larger bodies con- 
tained dark lateral masses connected with a semi-transparent tube. Still larger 
ones showed the dark masses completely separate. 
At present it is difficult to speak with any definiteness of the Up-to-date type 
of potato-anther degeneracy pending further investigation. : 
Heredity of Degenerate Pollen.—Dr. Salaman has found that ‘ the heredity 
of male sterility is distinctly dominant.’ 
It is hoped to determine, if possible, the extent to which the various types 
of degeneration described above are inherited. This year 300 seedlings have 
