K2.7

ראש תור – There are several
interpretations of this phrase and what shape it indicates.  The
רע"ב says a תור it is a type of
triangular women’s jewelry, and it is used to connote the corner of the wheat
field which protruded into the neighboring field of barley (fig.1).  The
רמב"ם also says ראש תור
connotes a triangular shape, meaning that the part of the
wheat field that comes into contact with the barley field is a corner; however
he appears to hold that the point of the ראש תור
merely touches the edge of the barley field, not that it actually extends into
it (fig. 2, see also תוספות אנשי שם regarding this
distinction; see also fig. 3 which is an illustration provided by the ב"ח
who seems to follow the same interpretation of ראש תור
as a corner, albeit situated differently).  The ר"ש
and מהר"י בן מלכי צדק on the other hand, seemingly
read the ת of תור to be a
ש as in שורה, or row, and
interpret our משנה as referring to the last row in the
wheat field, which has extended into the barley field (fig. 4).  The
רא"ש also changes the ת to a
ש, but he reads it as ראש שור, or
the head of an ox.  According to him, our משנה is
referring to where the ox which plowed the wheat filed reached the end of a row
turned around to plow the next row.  While turning the plow behind it, the
ox’s head extended into the barley field, creating an obliquely shaped
protrusion of the wheat field into the adjacent field of barley (fig. 5).
מפני שהוא נראה כסוף שדהו – Due to it’s distinctive
shape, the רע"ב says it is clear to all observers that
this wheat was planted separately from the barley.  מותר לסמוך לו
מאותו המין – Two fields owned by two different
people may be planted with different crops even though they are adjacent to each
other; the רמב"ם says that this is because the
פסוק  says שדך לא תזרע כלאים,
which implies that the אסור only applies to one
person’s field.  The משנה
is adding that because of this, if one can plant another species next to their
wheat in such a way that it looks like it is merely a part of his neighbor’s
field (according to the רמב"ם, by connecting it to his
neighbor’s field – see fig. 6), that too is permissible.  מותר
לסמוך לו תלם של פשתן – According to the
רמב"ם and the רע"ב single row of
flax is not profitable, and so an observer would realize that is was planted not
for the benefit of the crop, but rather to test the field’s suitability for a
future crop of flax; the רא"ש says the observer will
come to this conclusion because flax harms crops that are adjacent to it.
 In addition, תוי"ט notes that
this must be his actual intent, and, as shown by
R’ Yose at the end of the משנה, the
ת"ק allows this only at the edge of the field. 
ולא תלם של מין אחר –
Because any other crop is profitable even when there is only one row, even if it
was planted with the intent to test the field for that crop, since it appears as
if it is for the benefit of the crop, it is forbidden. 
ר"ש אומר
אחד זרע פשתן ואחד כל המינין – According to the
רמב"ם and the רע"ב, R’ Shimon is
being stricter than the ת"ק and forbidding flax as
other species are forbidden; according to theר"ש and
the רא"ש he is being lenient, and allowing test rows
of other crops just as the ת"ק allows a test row of
flax.