As mentioned above, this succulent is capable of great improvement by
careful selection of seed from the best stalks. The old Purple Top
variety is no longer grown, its place having been taken by the larger
shoots and better quality of the variety known as Conover’s Colossal.
This latter, however, has been propagated so extensively and with so
little care that it is now almost impossible to obtain seed or plants
that will produce the splendid shoots of the original stock. Of the new
varieties Barr’s Mammoth seems to be the most promising, and as grown
in some fields in the vicinity of Philadelphia produces shoots which
will average nearly an inch in diameter.