J 8 PITS ELEMENTARY FIBRE. [BOOK i. 



and apparently quite uncoloured as through a true opening. 

 But when I used the strongest of Arnicas objectives, which 

 can only be employed advantageously in a few cases, and to 

 very delicate and transparent objects, but which, with the 

 same ocular, gives a magnifying power of 500 diameters, 

 every doubt was dissipated as to whether a membrane was 

 stretched over the dot or not, since such a membrane was now 

 plainly to be perceived: it was, indeed, very transparent, 

 but small granules, &c., were distinctly to be seen adhering 

 to it. If this was not to be mistaken in the preparation 

 which was lying in water, the result of the examination of 

 dried preparations was yet more decisive, since no doubt was 

 longer possible as to the presence of a closing membrane, and 

 of the bright violet colouring of the same." Mohl then goes 

 into a variety of evidence in support of the general opinion 

 that membrane is originally imperforate, for which the 

 reader is referred to the excellent translation of his paper 

 in the Annals of Natural History, vol. xviii. p. 148. It will, 

 however, be hereafter seen that full-grown cells are occa- 

 sionally pierced by loop-holes of such considerable diameter 

 as to permit the passage of animalcules through them. (See 

 page 46.) 



Elementary Fibre may be compared to hair of inconceivable 

 fineness, but it is extremely variable in size. In Pleurothallis 

 ruscifolia, where it is large, I find it -g-oVo* i n Crinum amabile, 

 where it is middle sized, 7 9 \ of an English inch in diameter. 

 It has frequently a greenish colour, but is more commonly 

 transparent and colourless. It appears to be sometimes 

 capable of extension with the same rapidity as the membrane 

 among which it lies, and to which it usually adheres ; but 

 it occasionally elongates less rapidly, when it is broken 

 into minute portions, and is carried along by the growing 

 membrane. In direction it is variable (Plates I. and II.) ; 

 sometimes it is straight, and attains a considerable length, as 

 in some fungals; sometimes it is short and straight, but 

 hooked at the apex, as in the lining of the anther of Campa- 

 nula ; occasionally it is straight, and adheres to the side of 

 membrane, as in the same part in Digitalis purpurea ; but its 



