32 
THE AMERICAN BOTANIST. 
apparently not dead, it is supposed that they would 
start into growth the next season. 
So it seems that the gentian seed does not differ from 
that of certain other plants in being able to retain its 
vitality through periods of adverse conditions, and yet 
spring into life when these are replaced b^^ others that are 
favorable. It is not improbable that this dormant exist- 
ence may, in the case of some of the seeds, precede by a 
season or two the final awakening of their vitalit}^, as 
commonly happens with the seeds of many other plants. 
Aikin, Md. 
MAT PLANTS. 
Mat plants are plants with numerous prostrate 
branches which are usually closely crowded and form a 
more or less circular body a few inches to eight or more 
feet in diameter. This prostrate discoid body habit is 
quite characteristic of a small number of plants belonging 
to various families. Among the most typical mats may 
be mentioned Amaranthus hlitoides, Portulaca oleracea, 
Euphorbia maculata and Euphorbia serpyUifolia. Mats 
are usually annual plants either of the ordinary herbace- 
ous type or very fleshy. There are, however, a number of 
geopHilous perennials which form mats, like Fer^ena 
bracteos^. The main radiating branches usually give rise 
to numerous smaller branches and they may or may not 
strike root. In the niore typical cases there are no roots 
except the main central root. Mats are especially char- 
acterized by having a large number of small leaves, seeds, 
and flowers. There peculiarities, of course, harmonize 
with the shape and position of the plant. 
Like most ecological groups, mat plants intergrade 
with other types of body habit. On the one hand they 
pass over into such forms as Malva rotundi folia ^ CaUir- 
rhoe involucrata, Citrullus citrulus, and the typical 
carpet plants ; and on the other, transitions occur 
between them and tumble-weeds or even normally erect 
forms. Although it is not intended to give a definition 
