﻿270 Evans: The genus Plagiochasma 



dichotomous androecia occasionally found in Lunularia, where 

 two growing points are involved (i8, p. 26). They represent, 

 according to his ideas, a persistence of the two-Iobed condition 

 at the apex of an ordinary thallus, where the single growing point 

 lies in the indentation between the lobes. Kashyap (15, pp. 318, 

 321), however, says that in both P. appendiculatum and P. ariicu- 

 latum the androecium usually has two growing points and implies 

 that the horseshoe shape is therefore due to a forking. Un- 

 fortunately, he presents no conclusive evidence to support his 

 position. The antheridia are of the usual marchantiaceous type. 

 Each one lies at the bottom of a deep depression, the roof of which 

 forms a distinct bluntly conical ostiole with a minute opening at 

 the tip. Between the ostioles the epidermis of the androecium 

 shows numerous pores and these, as recently demonstrated by 

 Kashyap, are of the same type as in the vegetative thallus. In 

 cases where the normal pores are complex and show many radiating 

 series of cells with several cells in each series, the androecial pores 

 tend to be more simple and to show fewer series of cells and fewer 

 cells in each series. A row of delicate and slender scales, usually 

 pigmented with purple, surrounds the androecium. 



The carpocephala arise singly or in short median rows from 

 the dorsal surface of the thallus and apparently in most cases 

 neither stop nor interrupt its further elongation. Each carpo- 

 cephalu mcommonly bears three or four archegonia evenly dis- 

 tributed around its margin (Leitgeb, 18, p. 29) although in P. 

 appendiculatum, according to Kashyap, the number is frequently 

 five or six and may be as high as nine. Through the extensive 

 growth of the upper median portion and of the parts adjacent to 

 the archegonia, the latter are displaced to the lower part of the 

 carpocephalum and each one eventually lies at the bottom of a 

 groove which is bounded by two folds of tissue. In case fertiliza- 

 tion has taken place the grooves become much deeper through the 

 continued growth of the folds, the edges of which come together 

 and grow inwards toward the developing sporophyte, as originally 

 described and figured by De Notaris in the case of P. rupestre 

 (S, p. 480, pi. I, f. 20-26) ; where the folds meet at their upper 

 ends they form a more or less distinct apiculum or horn. No 

 pseudoperianths of any sort are developed. Around the margin 



