292 QUARTERLY CHRONICLE OF MICROSCOPICAL SCIENCE. 



pheral portions, entailing a more and more sharply expressed 

 differentiated origin of the lateral buds from unequivalent 

 elements of the tissue. 



In the smaller Sphacelarie(E, growing with an apical cell, 

 the origin of the thallome-branches does not appear connected 

 with any definite position. In the further advanced links 

 of the series [Halopteris, Stypocaidon, Cheetopteris) the dif- 

 ferentiation of the purely vegetative branch-forms become 

 more considerable, but still exhibits numerous transition- 

 stages. Also the thallome-torms originate at definite places 

 of the mother-axis ; but still the places of origin of the 

 thallome-forms are common to several of them. Adven- 

 titious buds make their appearance besides the normal rami- 

 fications. 



In the most highly differentiated terminal links of the series, 

 the Cladostephus-species, we finally see all these differen- 

 tiations of the thallome-forms constant, and their place of 

 origin definite. With the differentiation, also the variety of 

 the thallome-forms has increased. Normal ramifications and 

 adventitious buds, leaves and fruit-leaves, fruit-branches, 

 hairs and root-threads, occur as completely individualised 

 and strictly distinct thallome-forms, and each of these 

 has its separate place of origin. In Cladostephus the normal 

 ramifications proceed from dichotomy of the apex, the 

 adventitious buds from the central cells of the axis, the 

 leaves from the oldest cortical cells, the fruit-leaves — that'is 

 to say, a higher stage of the leaf- metamorphosis — from the 

 youngest cells of the cortex, the hairs from the apex of the 

 tip of the leaf, the fruit-branches from the joints of the 

 fruit- leaves. 



ii. Cladostephus verticillatus is a perennial whose buds 

 possess a normal vegetation-pause, just like shrubs and trees. 

 It consists of a system of dichotomously branched stems 

 beset by numerous many-jointed whorls of leaves. The 

 stems and leaves grow by successive subdivisions of their 

 apical cells. By the division of these primary joint-cells 

 secondary joint-cells are formed by means of walls following 

 each other in definite sequence and direction ; in this way 

 also the tissue of the joints is differentiated into medulla and 

 cortex. 



In the production of branches by dichotomy the apical cell 

 is divided into three portions — two new apical cells and a 

 terminal portion of the old axis. A portion of the apical cell 

 is first cut off by a septum directed obliquely and laterally 

 from its apex. This newly formed cell is the mother-cell of 

 one of the commencing bifurcations. In the remaining por- 



