Every such map or plat shall particularly set forth and describe such portion of the government survey as is intended to be platted, and when the premises cannot be accurately described by legal subdivisions, then the boundaries thereof must be defined by metes, bounds, and courses. Such map or plat shall also specify and describe all the public grounds, except streets and alleys, by their boundaries, courses, and extent, and all streets and alleys by their courses, length, widths, names, or numbers, by writing or figures upon that portion of the map or plat intended for those uses. All the lots intended for sale may be numbered either by progressive numbers, or, if in blocks, progressively numbered in each block, and the blocks progressively numbered or lettered. Where all the lots in any block are of the same dimensions, it shall be sufficient to mark the precise length and width upon one tier thereof, but all gores, triangles, or other lots, either squares or parallelograms, shall have the length of their sides plainly defined by figures.