582 
Journal of Agricultural Research 
Vol. XXVI; No. i* 
gregated. The development of mycelium below the uredinium and 
through the interior of the leaf is less massive than in Baart. The 
mycelium from one surface of the leaf to the other is empty. Even the 
basal cells of the uredinium itself are nearly empty. Many spores have 
been formed and liberated, as the withering stalks attest. A few spores 
still remain and show the usual heavy walls with minute warts, and the 
four equatorially-placed germ pores. Tittle further growth and spore 
production would be expected from this part of the uredinium, however. 
Effect on Nuclei and Plastids 
The results of a study of nuclei and plastids in infected Kanred tis¬ 
sues, similar to that of Baart, are given in Table III. The same methods 
and magnifications are used. 
In comparing these with those of Baart, the first point that comes out 
clearly is that both nuclei and plastids in the leaves of healthy Kanred 
seedlings are decidedly smaller than in Baart. The figures for the 
normal Kanred nucleus are 90 by 70. It is small, dense, and rounded. 
In Baart the nucleus is 115 by 70. The average healthy Kanred plastid 
is 45 or 50 by 25, as opposed to 60 by 25 in Baart. 4 
Under the conditions of this experiment, at least, Kanred nuclei 
expand rapidly at the center of an infection, attaining the maximum size 
a week after inoculation. The percentage increase in volume appears 
to be about the same as in Baart. The outlying districts of the infection 
are affected much sooner here than in Baart. Even at the margin of the 
mycelium and beyond it, the nuclei are beginning to undergo the same 
change. The figures seven days after inoculation (Table III, nuclei 7b) 
130 by 88 at the center of the infection, 111 by 71 at the margin, and 101 
by 71 just beyond the fungus, as opposed to 87 by 71 at the end of the 
same section, show clearly the rapid radial spread of this effect of the 
fungus. 
By the ninth day, when the uredinia are breaking the epidermis, a 
few of the centrally located nuclei have collapsed and are flattened or 
irregular in form. A few of the nuclei live on, even in older material, 
but the majority at the center and some in outlying regions collapse and 
stain a dense uniform red in which no trace of nuclear net remains. 
* Figures in this and the following paragraph are the sums in millimeters of the two diameters of io nuclei 
or plastids X 1130. 
