42 
LOUIS OTTO KUNKEL 
The nucleus enters the sporidium when it has reached approximately 
one half the size that it will be when mature. In passing through the 
sterigma the nucleus becomes very much elongated, as shown in figure 
12. This elongated nucleus soon becomes spherical again and takes 
a position near the center of the sporidium. The mature sporidium 
contains all or almost all of the protoplasm from the promycelial cell 
which is left practically empty. Generally the sporidium falls from 
the sterigma before its nucleus begins to divide, but sometimes, as 
shown in figure 13, nuclear division occurs while it is still attached to 
the sterigma. Nuclear division may occur in the sporidium, either 
before or after germination. It is, however, generally binucleate at 
the time it germinates. It produces either a germ tube or a sterigma- 
like outgrowth on which is borne a secondary sporidium. Figure 14 
shows a mature sporidium in which nuclear division has not yet 
occurred. The nucleolus is shown outside of the nucleus in this figure. 
T(^is is probably the result of fixation, since the nuclei in many of the 
sporidia contain nucleoli. Figure 15 shows a sporidium which contains 
two nuclei. 
It is worth noting that if the aecidiospores are immersed in water 
rather than floated on its surface, they produce long tubes which are 
often devoid of septa. Such promycelia seldom produce sporidia 
and might easily be mistaken for ordinary aecidiospore germ tubes. 
In cultures as much as two days old, these tubes regularly contain 
four nuclei . A study of earlier stages of germination shows that these 
four nuclei arise through two successive divisions of a single nucleus. 
This observation establishes the promycelial nature of these germ 
tubes also. They are therefore not to be confused with the germ tubes 
of ordinary aecidiospores. Werth (20) observed similar non-septate 
germ tubes when he immersed the aecidiospores of Endophyllum sem- 
pervivi in water and is inclined to the view that under these conditions 
the aecidiospores produce ordinary germ tubes rather than promycelia. 
My observ^ations suggest that a cytological study of the aecidiospores 
of E. sempervivi which have been germinated under water will show 
that they produce only promycelia. Maire (12) claims to have found 
a variety of E. sempervivi {E. sempervivi variety aecidioides R. Maire) 
with aecidiospores that regularly produce germ tubes rather than 
promycelia, but it is possible that a further study may show that these 
germ tubes also are in reality promycelia. 
In the light of the facts described, there can be no doubt that 
