14^ 



LECTURE IX. 



distinguished from the rest of the fundamental parenchyma by possessing much 

 smaller intercellular passages, or none at all, and by the walls being strongly 

 lignified. The same is the case with the brown strands of the Bracken-fern, which 

 are prosenchymatous, it is true, but in part contain starch. The stem oi Lycopodiiim 

 chamcBcyparisms (Fig. 157) shows that under certain circumstances the main mass of the 

 fundamental tissue may assume the sclerenchymatous condition : the very thick-walled 



cells, figured in transverse section, 

 are pointed above and below, and 

 are arranged in prosenchymatous 

 layers. Not rarely, however, scle- 

 renchyma cells occur isolated, 

 or arranged together in small 

 roundish groups, or even forming 

 loose layers in the fundamental 

 tissue. Thus, the hard concre- 

 tions, about the size of a grain of 

 sand, in the soft flesh of the Pear, 

 consist of groups of very thick 

 sclerenchymatous cells, which are 

 apparently nothing further than 

 peculiarly developed parenchyma 

 cells. The same holds good of 

 the layers or groups of so-called 

 stone cells, beneath the layer of 

 cork in the cortex of dicotyle- 

 donous woody plants (e.g. in the 

 Poplar), In other cases, these 

 isolated sclerenchyma cells ex- 

 hibit more characteristic forms, as 

 in Fig. 1 5 7 3, which represents a 

 many armed, large sclerenchyma 

 cell from the leaf of a Camelia. 

 Similar forms are found in the 

 cortex of some Conifers ; very fine 

 and numerous, for example, in 

 the Fir {Abies pectinafd). In 

 the hard stiff leaves of the Pro- 

 ieacecB and some other evergreen 

 plants, sclerenchymatous cells of 

 the most various form are to be 

 met with. Also in the pith of 

 ouped, lignified sclerenchyma cells occur, mostly 



Fig. 



a. h 



-Transverse section from the rhizome of Pteris aquili 

 root-hairs ; c strongly thickened brown walled cells beneath the epidermis ; 

 q a more deeply situated cell, less thickened— part of the wall seen en face, 

 se cells of deeper layers containing starch, passing over to the internal colour- 

 less parenchyma of the fundamental tissue. 



some wood plants, isolated or 

 however of simple form. 



If possible, yet more various than in the shoot-axes and leaves, are the forms of 

 fundamental tissue developed in the fruits and seeds of the Phanerogams. To select 

 only a few examples from the almost endless variety, it may be mentioned that the 



