164 AMERICAN JOURNAL OF BOTANY [Vol. io, 
-. 1905. The structure and development of mosses and ferns. Second edition. New 
York, 1905. Also third edition. New York, 1918. 
Clapp, G. L. 1912. The life history of Aneura pinguis. Bot. Gaz. 54: 177-193. Pis. 
IX-XII. 
Durand, E. J. 1908. The development of the sexual organs and sporogonium of Marchantia 
polymorpha. Bull. Torrey Bot. Club 35: 321-335. Pis. XXI-XXV. 
Florin, R. 1918. Das Archegonium der Riccardia pinguis (L.) B. Gr. Svensk Bot. Tidskr. 
12: 464-470. 
Garber, J. F. 1904. The life history of Ricciocarpus natans. Bot. Gaz. 37:161-177. Pis. 
IX, X. 
Grim, C. 1914. Monographische Studien an Treubia insignis Goebel. Flora 106: 331- 
392. Pis. III-V. 
Hartman, E. C. 1918. Development of the archegonium of Sphaerocarpos Donnellii. 
Unpublished thesis, Univ. of Wis. 
Haupt, A. W. 1918. A morphological study of Pallavicinia Lyellii. Bot. Gaz. 66: 524- 
533 - Pis. XX-XXIV. 
-. 1920. Life history of Fossombronia cristula. Bot. Gaz. 69: 318-331. 
-. 1921. Gametophyte and sex organs of Reboulia hemisphaerica. Bot. Gaz. 71: 
61-74. 
Humphrey, H. B. 1906. The development of Fossombronia longiseta , Aust. Annals 
Bot. 20: 83-108. Pis. V, VI. 
Hutchinson, A. H. 1915. Gametophyte of Pellia epiphylla. Bot. Gaz. 60: 134-143. 
Pis. I-IV. 
Janczewski, E. 1872. Vergleichende Untersuchungen iiber die Entwickelungsgeschichte 
des Archegoniums. Bot. Zeit. 30: 378-394. 
Kny, L. 1863. Beitrage zur Entwickelungsgeschichte der laubigen Lebermoose. Jahrb. 
Wiss. Bot. 4: 64-100. Pis. V-VII. 
Leitgeb, H. 1877. Untersuchungen iiber die Lebermoose. Heft III. Jena. 
MacVicar, S. M. 1912. The student’s handbook of British Hepatics. Eastbourne. 
Moore, G. T. 1903. Methods for growing pure cultures of algae. Jour. Appl. Micr. 6: 
2311. 
Rojas, H. 1918. Development of the archegonium and sporophyte of Sphaerocarpos tex- 
anus. Unpublished thesis, Univ. of Wis. 
EXPLANATION OF PLATES 
All figures were drawn from stained sections with the aid of an Abbe camera lucida, 
using Leitz objectives and oculars, and were reduced in reproduction to the magnifications 
indicated; Plate XVI being reduced three fifths, Plates XVII-XIX one half. 
Plate XVI 
Fig. 1. Horizontal section of a part of the apical region of the thallus showing the 
apical cell (a) in process of division. X 160. 
Fig. 2. Vertical longitudinal section of secondary segments ( b' and c) formed by 
the division of a primary segment; serial section adjacent to and following the one shown in 
figure 3. X 160. 
Fig. 3. Median vertical longitudinal section of the apical region of a vegetative 
branch of the thallus showing apical cell (a). X 160. 
Figs. 4-8. Successive serial transverse sections of the apical cell (a), and of the 
adjacent cells in a vegetative branch; b' and c at the right in figure 4 probably represent the 
anterior ends of cells formed from the youngest segment of the apical cell; c, d, e, and e' 
at the left in the same figure probably represent the anterior ends of the forward tier of cells 
formed from the second youngest segment. X 160. 
