18 CONNECTICUT GEOL. AND NAT, HIST. SURVEY. [Bull. 
THE ANTHOCEROTALES 
The Anthocerotales are sometimes called Hornworts or 
Horned Liverworts, and embrace the single family Anthocero- 
tacee. This includes only three recognized genera, two of 
which are represented in Connecticut. In spite of its small 
size, the order is of especial interest to the student of plant 
morphology and evolution, because it probably represents, more 
closely than any of the other existing Bryophytes, the ancestors 
.of the Pteridophytes. The northern species are all annuals, 
and make their appearance in May or June in wet pastures, 
along roadsides, or on wet rocks. Each gametophyte has 
several sporophytes growing from it; they begin to develop 
late in the summer, and continue in many cases until the 
plants are killed by the frost. 
The gametophyte is a thallus, sometimes bearing irregular 
and crispate outgrowths on the upper surface or along the 
margin, but never definitely divided into stem and leaves. The 
thallus branches by forking, but the forks are so close together 
that it soon assumes the form of a fleshy circular disc with 
many growing points scattered along the margin. It ap- 
parently absorbs throughout its entire surface, and is attached 
to the soil by means of thin-walled rhizoids, similar to those 
of the first type in the Marchantiales. The thallus shows but 
a slight degree of cell differentiation, but some of the species 
develop minute intercellular spaces, which, however, may con- 
tain slime as well as air., The green cells are characterized by 
the presence of a single large chloroplast in each. This is 
in the form of a plate with thin and irregular margins, lying 
close to the cell wall. Cells of this type are found nowhere 
else among the Bryophytes, and probably represent a primitive 
characteristic, indicative perhaps of a distant relationship with 
the green Alge. In all the other orders each green cell con- 
tains a number of small, disc-like chloroplasts, and agrees in 
structure with the green cells of the higher plants. Taking 
it as a whole, the gametophyte in the Anthocerotales is even 
more primitive than in either the Ricciacee or Metzgeriacez. 
Even the archegonia, although showing essentially the same 
structure as in the other Bryophytes, are imbedded in the 
