and some other Grasses. 459 
the arrangement of the stones which form the arch of a bridge. This coat 
appears to answer to the testa of the seed, and also to the external or purple 
one of the ergot, the colouring matter it contained having assumed a deeper 
Shade: this is made probable as there is observed on the exterior of some 
ergots what appear to be the remains of the pericarp, which adheres in irre- 
gular little filmy pieces, and are occasionally seen external to the purple layer 
when sections are viewed under the microscope with strong powers and trans- 
mitted light, as in Tas. XXXIII. B. fig. 1. ‘This happens when all the peri- 
carp is not lifted up on the apex. Leveillé, however, and some others have 
not been able to discover any coat ; for the former (op. cit. p. 573.) says, * On 
ne remarque pas de membrane à sa surface: les auteurs disent qu'il n'en existe 
pas, et en effet nous n'en avons jamais pu demontrer l'existence," 
On applying very high magnifying powers to thin sections of the central 
part the structure is seen to be distinctly cellular, the cells however being 
very small, and in the rye about four times less than those of the healthy 
grain. Their arrangement is by no means regular, there being many varia- 
tions in shape and size, as in Tas. XXXIII. B. fig. 1., which is a transverse slice, 
but in the longitudinal (fig. 2.) they have a greater tendency to be arranged 
in rows. Their contents likewise vary, some cells having one granule, appa- 
rently of an oily nature, which completely fills them, as in figs. 1. & 2.; 
others having two or three small ones, placed sometimes in the centre, as 
Phoebus observed; and others having granules which appear not oily, but 
very like the minute particles that are seen to be mingled with the fecula in 
the healthy grain. 
The purple coat is not, as Phoebus figures it, composed of elongated cellular 
tissue, but of minute square cells, arranged in longitudinal rows between striæ 
or thicker places in the covering of the ergot, which may easily be mistaken 
for elongated cellular tissue, if a very high magnifying power be not used in 
the observation. 
The terminal point or cap of the ergot, when examined microscopically, 
appears to be a heterogeneous mass of structure; being composed externally 
of the cerebriform coating of withered pericarp and of the sporidia, which 
cements together the various hairs that are found on the exterior of the grain, 
and wbich incloses likewise what is conceived to be the remains of the peri- 
