292 CONSERVATIVE ORGANS. [LECT. VII. 



stems is destitute of vessels * ; for their presence, 

 at least in the stipes of the Mushroom tribe 

 (Fungi), and the stalks of many of the Algse, is 

 demonstrable by placing a small transverse slice 

 of any of them under a powerful microscope. 

 They are not, indeed, so readily distinguished in 

 a longitudinal slice, a circumstance which I am 

 inclined to ascribe to the transparency of their 

 coats confounding them with the cellular sub- 

 stance in which they are imbedded ; and which 

 consists of continuous, oblong cells, the membrane 

 forming the sides of which is of very different 

 degrees of thickness ; but, nevertheless, they 

 may be made out by any one accustomed to the 

 use of the microscope. I have never been able to 

 satisfy myself of what description these vessels are, 

 although it is evident, as Mirbel remarks, that 

 they are neither the spiral, nor the annular ; but I 

 suspect them to be the moniliform. The epidermis, 

 which cannot be separated from the cellular mass 

 it covers, is pierced with imperceptible pores, but, 

 according to Mirbel, it has no miliary glands. In 

 the different tribes of plants which afford examples 

 of this description of stems, the reproductive or- 

 gans are either altogether deficient, or so ob- 

 scure as to have eluded the researches of phyto- 



* Vide Element de Phys. veget. l ere Partie, p. 37 ; and Journ. 

 de Botanique, torn. iii. p. 36* 



