36 GENERAL DIFFERENTIATION OF THE PLANT-BODY 



with an instructive illustration of the different gradations of form amongst 

 individual organs. As we can here only refer to a few examples we must 

 limit ourselves to the formation of the branches. 



In the genus Sphacelaria itself the plant consists of axes which are built up 

 out of many rows of cells. They branch, producing many lateral branches which 

 in some species are all alike, in others appear as short shoots and long shoots. 

 They possess also ' hairs,' that is to say, outgrowths of limited growth which 

 remain as simple row r s of cells poor in protoplasm and are laid down in a different 

 manner from the ordinary branches, inasmuch as they arise so near the apex of the 

 axis that at their origin the apical cell is pushed to one side. In Halopteris 

 filicina the 'hairs' are wanting (Figs, n and 12), and the richly-branched 



FIG ii. Halopteris filicina. Shoot-system. The darker parts at the ends of the shoots are the apica cells. 

 From a micro-photograph. Slightly enlarged. 



thallus is composed entirely of long shoots and short shoots of different orders. 

 They are all, as is shown in Fig. 12, laid down in like manner quite close to the 

 apex. Each shoot ends in an apical cell, and is usually distichously branched so 

 that a feather-system of branching is produced. The branches of different order 

 are distinguished by the fact that the higher a shoot is in the order of branching 

 the smaller is its apical cell and the earlier does it end its growth and pass into the 



lungen, Bd. i. ; Magnus, Zur Morphologic der Sphacelarieen, in Festschr. zur Feier des hundertjahrigen 

 Bestehens der Ges. naturforsch. Freunde zu Berlin, 1897; Reinke, Beitriige zur vergl. Anatomic 

 und Morphologic der Sphacelariaceen, in Biblioth. botanica, Heft 23. 



