CH. VI. 



THE BRYALES 



189 



as a papilla which grows out into a filament ; or the endospore 

 sometimes 'grows out in two directions, and one of the papill?e 

 remains nearly destitute of chlorophyll and forms the first rhi- 

 zoid. The growth of the protonemal filaments is strictly 

 apical, no intercalary divisions taking place except those by 

 which lateral branches arise. If abundant moisture is present, 

 the protonema grows with great rapidity and may form a dense 

 branchinof al^'a-like growth of considerable extent. Sooner or 

 later upon this arise the leafy gametophores. The develop- 

 ment of the latter, as we have seen, also takes place abundantly 



Fig. 97. — Funaria hygrometrica. A, Fragment of a protonemal branch with a young 

 gametophoric bud; r, rhizoid; B, median optical section of the bud; C, older bud — • 

 I, surface view; 2, optical section; .v, apical cell; U, protonema with a still older 

 gametophore {gam) attached. A-C, X-225; D, X36. 



from the secondary protonemal filaments which may be made to 

 grow from almost any part of the gametophore. 



The development of the bud is as follows. From a cell of 

 the protonema a protuberance grows out near the upper end. 

 This is at first not distinguishable from a young protonemal 

 branch, but It very soon becomes somewhat pear-shaped, and 

 instead of elongating and dividing simply by transverse walls, 

 the division w^alls intersect so as to transform it into a cell mass. 



