74 



BOTANY. 



(e) The seed-coat of Eehinoeystis lobata is composed almost entirely 

 of sclerenchyma (Fig. 60). Tlie cell-walls are greatly thickened, and 

 the cells are very closely packed together, so much bo that all are 

 sharply prismatic (Fig. 61). 



102.— Fibrous Tissue. This is composed of elongated, 

 tbick-walled, and generally fusiform elements, the fibres 

 (Figs. 63 and 63), whose walls are usually marked with 

 simple or sometimes bordered pits. These elements in cross- 

 section are rarely square or round, but most generally three 

 to many-sided. They are found in, or in connection with, 

 the fibro-vascular bundles of Pteridophytes and Phanero- 

 gams, and give strength and hardness to their stems and leaves. 



7 



t^ 



Pig. 62. Fig. 63. 



Fig. 63.— Wood fibres of Aca- dasyearpum. isolated by Schnlze's maceration, a, 

 four fibres, X 95 ; S, a portion nf a fibre, x S30, showing the diagonally placed elon- 

 gaied pits ; c, the ends of eleven united flbns, X 95. 



Fig. 63.— Baat fibres of .Acer (?a«yca?p!/m. ii-olated by Schnlze's maceration, li, » 

 fibre, X 95 ; S, a portion of a fibre, X 230, showing Ihe much-thickened wall. 



Two varieties of fibrous tissue may be distinguished, viz., 

 (1) Bast (Fig. 63), and (2) Wood (Fig. 62). The fibres of 

 the former are usually thicker walled, more flexible, and of 

 greater length than those of the latter. In both forms the 

 fibres are sometimes observed to be partitioned.* 



* These partitions have generally been considered as formed aiibse- 

 quently to the fibres ; but it may well be questioned whether, in some 



