{Vol. 8 
104 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
‘ protection of the seed. The great majority, however, are defi- 
nitely perennial and some of these develop a considerable amount 
of woody tissue in their caudices. The eleven species which 
constitute the first group are further characterized by branch- 
ing stems, of which one is formed by the original terminal bud. 
An extreme development of the annual habit is certainly a defi- 
nite step in the direction of specialization, although probably a 
step of no great difficulty. Three species seem to belong to 
this group of extreme annuals, namely, L. recurvata, L. aurea, 
and L. Palmeri, and are placed higher in the scale of develop- 
ment than the first group. In these three species the stems are 
often branched but there is a distinet tendency to an unbranched 
condition; the terminal bud develops normally. The third cate- 
gory, those species which are definitely perennial, includes some 
thirty-seven species in varying degrees of development. The 
extreme development in this group is reached in certain arctic 
and alpine plants of which L. arctica and L. diversifolia are ex- 
amples. 
The rosette habit, in which the terminal bud remains unde- 
veloped and lateral stems arise from among the basal leaves, is 
characteristic of some thirty-three species. In many of these 
the rosette is strikingly symmetrical and approaches closely to 
the condition found in certain species of Physaria. Some inter- 
mediate steps in the formation of rosettes are of particular inter- 
est and indicate that the rosette may have arisen in several ways. 
In a few species, notably L. Engelmannii, the terminal bud pro- 
duces a short, sterile shoot. In L. lata and L. pinetorum the 
terminal bud gives rise to a short, fertile shoot that is floriferous 
nearly or quite to the base, in contrast to the longer lateral 
stems that bear an inflorescence above their numerous leaves. 
In L. intermedia and L. arizonica the terminal bud may give 
rise either to a normal fertile stem or may be completely inhib- 
ited. Branching stems are comparatively rare among the 
perennial species. 
At the top of a list in which the species are arranged in an 
order of merit based on specialization in the habit of growth is 
placed L. Cusickii. This plant is an annual or short-lived peren- 
nial which has evidently been derived from truly perennial 
