MICHIGAN ACADEMY OF SCIENCE. 
193 
Neither does the term rootstock as above defined apply with full force 
to that underground stem of the migratorial sunflowers which the de- 
scriptive botanists call a “creeping rootstock” by means of which the 
plants of this group are said to be perennial. Rootstocks proper differ 
from the so-called rootstocks of the sunflowers in the following essen- 
tials: The rootstock proper is indefinitely perennial; that of the sun- 
flower is a winter annual vegetatively produced each year and com- 
pletely dying the next, after having performed its work of the second or 
functional season as will be more fully discussed further on. The root- 
stock proper continually adds to its length at the apex by annual growth 
and dies off to an equal amount at the rear end and bears on its upper 
surface the scars of the aerial stems of several successive years. The 
somewhat similar structure in the migratorial sunflower which, in a 
degree, resembles the rootstock in structure and function, is an under- 
ground branch which does not possess several of the essential characters 
of the rootstock proper as defined in the books. 
It resembles the rootstock in having a progressive, forward, horizontal 
growth for but one season only, and has a terminal bud at the forward 
end which grows upward during the second season to form the aerial 
stem with its load of branches, leaves and fruit, and another individual 
like itself. The resemblance ends here, for, unlike the rootstock proper, 
it does not possess the following characteristics: It is not perennial, 
as is generally supposed, or even properly biennial (this statement will 
be considered infra) , hence they do not, after several years growth, 
die off annually at the rear end to an amount equal to that annually 
added by progressive growth at the front end, thereby retaining a con- 
stancy of length and this for an indefinitely long time; there are no 
annual stalk scars on its upper surface, indicating the age from the 
growing point back to the dying end. 
It furthermore is not a continuation of the previous year's growth 
as is the case with the rootstock but grows out from the underground 
portion of the aerial annual stalk of its own formative season ; this 
makes it a subterranean branch identical homologically with the similar 
structure in the potato and denies to it all rootstock characters. Hence 
the term “creeping rootstock” as applied to the sunflower should be forever 
discontinued. But we need a special term to be applied to this and iden- 
tical structures in other plants. A suitable term for this purpose is 
difficult to find or invent; but I must have some term from now on, 
and provisionally I shall use the good Anglo-Saxon compound earth- 
branch. I will cordially thank anyone who will send me a more suit- 
able term for future adoption. This earth-branch has all the characters 
of a branch, for it buds and branches itself like aerial branches. 
1 have made a seemingly contradictory statement above to the effect 
that the earth-branches of the migratorial plants are not perennial as is 
commonly supposed or even properly biennial This seems the more con- 
tradictory when we remember that this group of plants is placed under 
the classification of perennial. 
To reconcile this seeming contradiction I will proceed to give an ex- 
act statement of the life history of a single plant. We will begin with 
the seed, whose young plant as soon as it becomes established the 
first year, sends out an earth-branch. At the end of the first season 
