The Heterotrichous Habit in the Protonema of the Bryales

Abstract

DURING recent investigations on the development in aseptic culture of a range of typical representatives of the Bryales (species of twelve genera, from six orders) we have found that the protonema possesses a more definite morphological pattern than would appear to have been appreciated previously. Examination of the advancing edge of isolated cultures growing on a solid substratum (Knop's agar or filter paper moistened with Knop's solution) has shown that in all the species studied, with the one exception of the aquatic moss Cinclidotus fontinaloides (Hedw.) P. Beauv., there is a striking distinction between a horizontal system of filaments creeping in or on the substratum and an aerial system of filaments arising vertically or obliquely from the horizontal system. This “heterotrichous habit”, to use a term employed by Fritsch1 for the corresponding condition in the algae, is well seen in Funaria hygrometrica Hedw. (Fig. 1), in which the prostrate system of a well-developed protonema is formed by stout brownwalled filaments with oblique septa and few chloroplasts, while the filaments of the aerial system, on the contrary, have hyaline walls, straight septa and numerous chloroplasts.