66 MISSOURI BOTANICAL GARDEN BULLETIN 
down into the ground their full length without branching. 
If, therefore, the plants are taken up when the primary 
roots are still short and without lateral branches, transplant- 
ing, if carefully done, can be carried out with little or no 
injury. It is even better, however, to transplant before the 
new roots have started to grow from the rhizome, but in 
order to do this the plants must be moved immediately after 
the flowering season is over. 
It is important that the rhizomes be kept free from over- 
growths of other plants. Any smothering of this kind is 
almost certain to result in decreased vigor in the plants and a 
scarcity of flowers in the next season. All dead leaves that 
are easily detachable should be removed from the plants, but 
the practice of cutting back the green leaves because the ends 
have begun to turn yellow honid bot be indulged in. In the 
leaves is produced the food which later is stored in the 
rhizomes, and any decrease in the total leaf surface carries 
with it a corresponding reduction in the available food sup- 
ply for the next season’s growth and flower production. The 
iris, like most other plants, is subject to certain diseases, but 
of these none have assumed any great importance in and 
about St. Louis, and this phase of iris culture need, there- 
fore, not be considered here. 
HORTICULTURAL GROUPS OF THE IRIS 
German Iris.—These irises, all of which are hardy, are 
usually given as varieties of Iris germanica. However, the 
latter species has but very few varieties, the plants given as 
varieties usually being hybrids of Iris germanica with a 
number of other ies and garden forms, all of which are 
very closely related to the above species. The varied parent- 
age of the German irises accounts for the great variety of 
color in these forms, colors which range from pure white 
through all shades of mauve to blue and dark purple, and 
not infrequently flowers marked with yellow occur. The 
blossoms are large and handsome and are borne on stout, 
erect, branched stalks, much exceeding the clumps of spread- 
ing leaves. The larger part of the Garden collection in the 
greenhouses will consist of varieties of the German iris. 
_ Japanese Iris.—Although far outnumbering the German 
irises, the Japanese varieties offer none of the difficulties as 
regards parentage that the German irises do. Iris Kaemp- 
feri, sometimes known as Iris laevigata, is the only known 
percent of this group. The Japanese forms anti A flower 
ater than those of the preceding group, and while the color 
of the flowers also ranges from white to dark purple the 
