No. II.] THE BRYOPHYTES OF CONNECTICUT. 1 3 



sometimes so closely that it cannot be separated without injury. 

 It develops two types of rhizoids, both of which represent 

 simple outgrowths from cells. In one type the walls are thin 

 throughout; in the other they bear scattered local thickenings 

 in the form of short rods which project into the lumen. The 

 rhizoids are all short-lived, and those of the first type simply 

 anchor the plant to the substratum ; those of the second type, 

 however, by means of capillarity, play a certain part in the 

 process of absorption. In addition to the rhizoids, the thallus 

 often bears longitudinal rows of delicate scales on the lower 

 surface. These are developed very early and arch up over the 

 growing point, thus protecting it from injury. 



The thallus is more or less differentiated, and always shows, 

 at least in certain stages of development, a distinct epidermis, 

 beneath which the photosynthetic tissue is situated. The latter 

 consists of green cells loosely arranged with intercellular spaces 

 containing air among them. In the higher forms these cells 

 are in distinct air-chambers, which communicate with the out- 

 side air by means of pores in the epidermis. In the lower 

 forms they simply line the intercellular spaces, and the com- 

 munication with the outside air is often less definite. The 

 Marchantiales are divided into two families, the Ricciaceas and 

 the Marchantiacese, which differ from each other most 

 markedly in the structure of the sporophyte. 



The Ricciacese include both aquatic and terrestrial species, 

 and are usually smaller than the Marchantiacese. The ter- 

 restrial forms grow in old fields, along damp roadsides, and 

 on the muddy borders of ponds. The thallus, which rarely 

 attains a length of fifteen millimeters, forks repeatedly in 

 one plane, thus giving rise to a characteristic rosette. All the 

 New England species are annual, developing their sporophytes 

 in the autumn. The aquatic Ricciacese are larger than the 

 others, and rarely produce sporophytes, the tips of the thallus 

 being able to survive the winter. When they become ter- 

 restrial, they sometimes assume an appearance very different 

 from their normal aquatic state. 



The archegonia in the Ricciacese are so deeply immersed 

 in the thallus that only their necks protrude above the surface. 

 In consequence of this fact the sporophytes begin their 

 development beneath the surface, and they retain this position 



