LECT. VIII.] HOLLOW HERBACEOUS STEMS, 423 



spongy, lax, pith, the stem, when examined un- 

 der the microscope, displays every character of 

 the real ligneous stem; resembling particularly 

 that of the Elder, except that the cells of the di- 

 vergent rays in the Thorn Apple are nearly 

 square, whereas those of the Elder are oblong. 

 The stem of Thorn Apple is in fact a soft ligneous 

 stem ; and, consequently, has been hitherto in- 

 correctly classed as herbaceous. The softness of 

 the stem is no argument against this decision, and 

 only demonstrates the great diversity, with re- 

 spect to induration, which wood displays. 



B. Hollow herbaceous stems may, also, be de- 

 scribed under two subdivisions ; a. thejistulous or 

 unpartitionedy and b. the partitioned. 



a. In internal structure there is little to dis- 

 tinguish the Jistulous or unpartitioned hollow 

 stems from those of the last division, except the 

 deficiency of the pulp or pith which constitutes 

 the hollow ; some of them, in every other respect, 

 resembling closely the Bryony, or those of the 

 first subdivision ; and others those of the second. 

 With regard to the cavity in the centre of the 

 stem, in some it is apparently the consequence 

 of an original deficiency of cellular matter; for 

 that which exists has evidently undergone no com- 

 pression; whilst in others it is evidently com- 

 pressed, and the hollow seems to be the result 



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