July, 1922] DODGE STUDIES IN THE GENUS GYMNOSPORANGIUM 
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Im allgemeinen zeigt die Tiefe in den Geweben des Wirtes, den sich der Pilz zum 
Sitz seines Lagers ausgewahlt hat, eine gewisse Beziehung zu der phylogenetischen Ent- 
wicklung. 
In certain subfamilies pycnia are always subcuticular, other sori may 
or may not be so situated. In several genera all sori are subepidermal. 
Grove^ also believes that the placement of sori is an indication of the 
trend of evolution. The transference of the spores to a place either (i) 
beneath the cuticle, (2) in the epidermal cells, or (3) just beneath the 
epidermis, and their aggregation into definite sori would be advances in 
adaptation, ''and the most effective of all (the subepidermal sorus) is alone 
to be met in the highest groups." 
The writer^ investigated the origin of the teliospore in several of our 
common Gymnosporangia and found that here, unlike the condition in all 
other known rusts, the teliospores are formed from buds arising out of 
subterminal cells of the plectenchymatous primordium. After discovering 
that the telial sorus of G. clavipes is subcuticular, it was thought that it 
might differ in the origin of the teliospore from other Gymnosporangia 
and thus conform to the mode described for all other rusts. However, 
as will be shown later, here too the preteliospore degenerates, functioning 
only as a buffer cell just as it does in the other forms previously described 
by the writer. 
The Host-Parasite Relationship 
The first leaves of the actively growing shoot of the young red cedar are 
called subulate in contrast with the scale leaves formed later. The free blade 
is somewhat less than a centimeter long and the basal portion runs down 
on the stem about the same distance, varying according to the rate of 
growth of the stem. As there are three rows of leaves, a cross section 
of the stem shows the three decurrent leaf-base ridges. The parenchyma 
of these leaf ridges merges with that of the cortex of the stem, so that 
there is frequently no definite separating line (PI. XXII, fig. 3). 
The leaf is provided with stomata along its upper (proaxial) surface 
and on the abaxial side downward from a line about opposite the end of 
the resin duct, or a little above the line of the leaf axis. There is a single 
vein in the leaf. A layer, one or two cells thick, of stereome extends along 
the lower side next the epidermis and continues down the decurrent basal 
portion, being interrupted wherever stomata are present. 
In addition to the true cuticle, the common covering of the leaf and 
young stem, the epidermal cells are further provided with a layer which 
can easily be differentiated by proper staining. According to Von Mohl,^ 
the cuticular (cuticularized) layer as distinct from the true cuticle is that 
part of the wall of the cell which has a cellulose matrix impregnated with 
^ The British rust fungi, p. 79. 1913. 
^ Mycologia 10 : 182-193. 1918. 
^ Bot. Zeit., p. 502. 1847. 
