644 
Joumal of Agricultural Research 
Vol. XXVIII, No. 7 
sandy type common in low places in many Florida strawberry fields, the surface 
of the rotting area will of course appear blackish (PI. 1, A, C). If little or no 
soil clings to the berry, the true dark brown color of the rot will be evident 
(Pl. 1, D). The rot usually starts before the berry begins to turn red, some¬ 
times even before the fruit is a third grown (PI. 1, E). In this case the discolored 
side will be of a lighter brown, and only a little soil will adhere. An early attack 
on the berry will result in a deformed fruit, but as the rot progresses rather 
slowly, the upper side of the berry develops normally and ripens without showing 
rot, so that one can not tell that the berry is diseased until it is turned over. 
As a result many such berries are picked unintentionally and only extreme care 
will prevent their being overlooked by packers. 
Sections of the rotting berry show that there is a definite line of demarcation 
in the pulp indicating clearly how far the disease has spread. Where healthy 
and diseased tissues meet, the pulp is only slightly faded and brownish; otherwise 
the diseased area stands out sharply on account of its rich brown color. The 
rotted part later becomes dried out or mummified (Pl. 1, B). By using a hand 
lens one is able to see masses of hyphae which bind the particles of soil together 
and hold the dirt to the surface of the berry. It will be shown that these soil 
hyphae belong to the Rhizoctonia which is causing the rot. In a free-hand 
section of the browning pulp examined under the microscope can be seen vast 
numbers of hyphae crowding in between the cells in the more recently invaded 
regions (Pl. 2, B, a), while in those parts of the berry where the fungus has com¬ 
pleted its work the cells are crushed and distorted and the spaces are packed 
with felty masses of mycelium. If the affected part of the berry is cut away the 
remainder will be found to be perfectly edible (Pl. 1, C), Such rot fungi as 
Botrytis and Rhizopus grow through the berry and usually completely destroy 
it once they have gained a foothold. The appearance of berries attacked by the 
hard rot is such that they will be discarded wherever found. The rot develops 
so slowly that it would not be communicated rapidly to other berries under 
refrigeration in transit. 
Whether the fungus, as it advances between the cells, attacks only the middle 
lamellae, as is so frequently reported for other intercellular fungi, is uncertain. 
At first the cells of the invaded tissues actually become hypertrophied, conse¬ 
quently the intercellular hyphae are put under pressure and are compelled to 
force back the elastic cell walls as they advance (Pl. 2, B, c). Certainly water 
is not withdrawn from the pulp cells in mass, resulting either in a wet rot such 
as is produced by Rhizopus or in a separation or falling apart of host cells, such 
as follows the work of Pezizella. Water seems to be lost more by a drying 
out process. Cells in the decaying tissues gradually collapse after the period 
of swelling and the hyphae crowd in, becoming more and more intracellular. 
The feeding of the hyphae in the middle lamellae may be the cause of a sort of 
mucilaginous disorganization which is manifested by the presence of quantities 
of intercellular stainable substance which so often surrounds the hyphae. This 
is more noticeable as the disease progresses. Striae or laminations in the 
adjacent walls are then more distinct. The intercellular substance and the 
peculiar manner in which the mucilaginous layers are split apart are brought 
out in Plate 2, figure B, 6. The contents of the unstained hyphae are foamy or 
vacuolate. 
MYCELIAL CHARACTERS 
The mycelium of the fungus is comprised of, septate branching hyphae of 
fairly uniform diameter, though where a branch grows out the diameter is some¬ 
what less. In some cases hyphae are very coarse for short distances and branches 
are very irregular with blunt ends. The cells usually contain more than one 
