192 
THIRTEENTH REPORT. 
head the roots play no part in its differentiation. The so-called root- 
stock. or earth branch is the great character there. Hence we will speak 
of the underground systems as bases of fundamental grouping. I think 
that these systems have never before been nsed in the classification of 
these plants. 
The genus Helianthus is one of the most interesting and the least 
understood of all the genera of our Michigan flora. This genus can be 
arranged under two great divisions, annuals and perennials. As there 
are no annuals indigenous to Michigan, I shall give them no considera- 
tion in this article. 
The perennials persist for an indefinitely long time and can be classed 
under two heads, each containing many lesser groups. These two heads 
are strongly differentiated and are easily recognized by their different 
annual growth and methods of vegetative reproduction. In speaking 
of these heads it is necessary to have names for them, as I shall have 
occasion to refer to them frequently. I shall therefore, before describing 
them, give each group a name expressive of its most distinguishing 
character. The plants of the first head which T shall consider do not 
move about from place to place by an underground stem or shoot. Be- 
ing thus permanently located 1 have named it the Stationary Group. 
For the reason that the plants of the second head move about annually 
by means of an underground shoot or runner I have called it the Migra- 
tor ia l Group. 
The terms ‘‘stationary” and “migratorial” express two remarkably oppo- 
site and definitive characters in these groups. But each head has other 
characters as decidedly opposite and definitive as those above mentioned 
and strongly demand other names to be used synonymously and inter- 
changeably with those above given. Before going on with these group de- 
scriptions, I find it necessary to make a diversion long enough to give. con- 
sideration to the term “creeping rootstock” which is much used in the 
manuals in the description of the sunflowers to show the manner of their 
vegetative perennial perpetuation. The part denominated rootstock in 
this connection does not fulfill the definitions of the underground shoot 
of that name as given in the structural botanies, which is : A peren- 
nial, horizontally elongated, more or less subterranean, root-like form of 
the stem, which grows after the manner of ordinary stems, advancing 
from year to year, by the annual development of a bud at the apex, and 
emitting roots from the under surface; thus established, the older por- 
tions die and decay annually as corresponding additions are made to the 
opposite extremity. On these root stocks are seen the scars left by the 
aerial shoots of several years; in the spring the terminal bud unfolds 
into leaves and flowers, to perish in autumn, a new bud to open in the 
following spring, and a new internode, with its roots, to abide for seve- 
ral years. 
While the foregoing definition applies, in a degree, to the so-called 
rootstocks of the migratorial sunflowers, it is, in a high degree, inade- 
quate because it contains much more than belongs to the somewhat sim- 
ilar shoot of the plants which we are discussing. It does not apply 
in any degree to the stationary group as the latter has no shoots at all 
homologous to a rootstock although the botanists use the term root- 
stock in their descritions of the very few members of the group which 
they have known. 
