l8 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull. 



THE ANTHOCEROTALES 



The Anthocerotales are sometimes called Hornworts or 

 Horned Liverworts, and embrace the single family Anthocero- 

 taceae. 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 Algae. 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 Ricciacea or Metzgeriacese. 

 Even the archegonia, although showing essentially the same 

 structure as in the other Bryophytes, are imbedded in the 



