diff --git a/skimage/data/_binary_blobs.py b/skimage/data/_binary_blobs.py
index 83503151..e4a23984 100644
--- a/skimage/data/_binary_blobs.py
+++ b/skimage/data/_binary_blobs.py
@@ -21,6 +21,7 @@ def binary_blobs(length=512, blob_size_fraction=0.1, n_dim=2,
         Should be in [0, 1].
     seed : int, optional
         Seed to initialize the random number generator.
+        If `None`, a random seed from the operating system is used.
 
     Returns
     -------
diff --git a/skimage/transform/_geometric.py b/skimage/transform/_geometric.py
index 1cd5621f..71516faa 100644
--- a/skimage/transform/_geometric.py
+++ b/skimage/transform/_geometric.py
@@ -346,8 +346,6 @@ class AffineTransform(ProjectiveTransform):
 
     """2D affine transformation of the form:
 
-    ..:math:
-
         X = a0*x + a1*y + a2 =
           = sx*x*cos(rotation) - sy*y*sin(rotation + shear) + a2
 
@@ -574,8 +572,6 @@ class PiecewiseAffineTransform(GeometricTransform):
 class SimilarityTransform(ProjectiveTransform):
     """2D similarity transformation of the form:
 
-    ..:math:
-
         X = a0 * x - b0 * y + a1 =
           = m * x * cos(rotation) - m * y * sin(rotation) + a1
 
@@ -746,8 +742,6 @@ class SimilarityTransform(ProjectiveTransform):
 class PolynomialTransform(GeometricTransform):
     """2D transformation of the form:
 
-    ..:math:
-
         X = sum[j=0:order]( sum[i=0:j]( a_ji * x**(j - i) * y**i ))
         Y = sum[j=0:order]( sum[i=0:j]( b_ji * x**(j - i) * y**i ))
 
diff --git a/skimage/util/dtype.py b/skimage/util/dtype.py
index a0ff637e..d1108776 100644
--- a/skimage/util/dtype.py
+++ b/skimage/util/dtype.py
@@ -36,7 +36,7 @@ def dtype_limits(image, clip_negative=True):
     ----------
     image : ndarray
         Input image.
-    clip_negative : bool
+    clip_negative : bool, optional
         If True, clip the negative range (i.e. return 0 for min intensity)
         even if the image dtype allows negative values.
     """
@@ -67,9 +67,9 @@ def convert(image, dtype, force_copy=False, uniform=False):
         Input image.
     dtype : dtype
         Target data-type.
-    force_copy : bool
+    force_copy : bool, optional
         Force a copy of the data, irrespective of its current dtype.
-    uniform : bool
+    uniform : bool, optional
         Uniformly quantize the floating point range to the integer range.
         By default (uniform=False) floating point values are scaled and
         rounded to the nearest integers, which minimizes back and forth
@@ -284,7 +284,7 @@ def img_as_float(image, force_copy=False):
     ----------
     image : ndarray
         Input image.
-    force_copy : bool
+    force_copy : bool, optional
         Force a copy of the data, irrespective of its current dtype.
 
     Returns
@@ -308,7 +308,7 @@ def img_as_uint(image, force_copy=False):
     ----------
     image : ndarray
         Input image.
-    force_copy : bool
+    force_copy : bool, optional
         Force a copy of the data, irrespective of its current dtype.
 
     Returns
@@ -332,7 +332,7 @@ def img_as_int(image, force_copy=False):
     ----------
     image : ndarray
         Input image.
-    force_copy : bool
+    force_copy : bool, optional
         Force a copy of the data, irrespective of its current dtype.
 
     Returns
@@ -357,7 +357,7 @@ def img_as_ubyte(image, force_copy=False):
     ----------
     image : ndarray
         Input image.
-    force_copy : bool
+    force_copy : bool, optional
         Force a copy of the data, irrespective of its current dtype.
 
     Returns
@@ -381,7 +381,7 @@ def img_as_bool(image, force_copy=False):
     ----------
     image : ndarray
         Input image.
-    force_copy : bool
+    force_copy : bool, optional
         Force a copy of the data, irrespective of its current dtype.
 
     Returns