Cuscuta and its Host . 
681 
and plasticity of its walls. No connecting threads are present between the two adjoining elements, 
but they are always found in the transverse walls. A transverse wall is shown in which they have 
been converted into fine slime strings enclosed in callus rods, x 500. 
Fig. 51 A. Parts of the adjoining walls of two invading hyphae, near their tips. The walls are 
not yet fused together, but their surfaces appear to be becoming mucilaginous and stain with London 
blue. ■ x 800. 
Fig. gTB. A later stage, in which the adjoining walls are fused; the wavy blue line indicates a 
line of mucilaginous substance along which fusion has occurred. x 800. 
Fig. 51 c. A similar case, in which, however, the fusion line no longer stains with London 
blue. Faint indications of a blue stain are seen also on the inner edges of the two walls, x 800. 
(Figs. 51 A, B, €, from C. europaea on Vitisi) *■ 
PLATE L. 
(In Plates L and LI the drawings are obtained, unless otherwise specified, from 
C. reflex a on Salvia. | 
(Here, as also in PI. LI : H — host element; p = parasite element; hs — host sieve tube ; HC = 
host companion cell; sp. — space; x - broken or partly dissolved parasite wall; J = sieve plate at 
junction between host and parasite.) 
Fig. 52. Two invading hyphae which have just reached the pericycle of the host {Salvia). On 
the left the host element is merely slightly bulged inwards ; on the right the bulging has been carried 
further, and the wall of the pericycle cell (yj) has been absorbed as far as the middle lamella. f~ the 
remains of the wall of the last fibre, the rest of which has been absorbed. (Stained Delafield’s haema- 
toxylin.) x 750. 
Fig. 53. A similar invading hypha which has got through the greater part of the pericycle and 
has nearly penetrated into the phloem. Part of the wall over the tip of the hypha stained with 
London blue, x 500. 
Fig. 54. An invading hypha which has reached the old phloem ; the wall at its tip, where it is 
applied to the host sieve-tube wall, is still unaltered. It appeared at another focus that a continua¬ 
tion of this element went on further into the phloem. (Stained first in safranin and London blue 
and afterwards in Delafield’s haematoxylin.) x 600. 
Fig. 55. A somewhat similar case ; two adjoining hyphae in the host phloem. In the tip of the 
left-hand element the inner layers of the thick cell-wall are apparently beginning to be softened and 
stain in patches with London blue. (Stained as Fig. 54.) x 600. 
Fig. 56. Two invading hyphae in which the process of softening the wall appears to have pro¬ 
ceeded further, and the inner layer of the wall is swollen up and stains with London blue, x 600. 
Fig. 57 - Three similar elements which have penetrated still further into the host phloem; in 
two of them the whole thickness of the wall at the tip now takes the blue stain with London blue, 
x 450. 
Fig. 58. The tip of another such element, a thin outer layer of the wall still unstained. 
x 600. 
Fig. 59. A similar element near a lateral sieve plate (s) of the functional host phloem, to which 
it is very probable that it was about to apply itself. The relations of the walls were almost im¬ 
possible to make out ; it appeared that even at the tip a layer of unaltered parasite wall was still 
present, but was just being softened so as to stain with blue on the outer surface also, x 600. 
Fig. 60. A parasite hypha seen in transverse section making its way at right angles to the old 
host sieve tubes and going straight through a hole made in one of them. The wall of the hypha 
stains blue in parts, the section being probably taken near its tip. x 500. 
Fig. 61. The surface view of an invading hypha ; the wall as yet only stains blue in patches, 
x 600. 
Fig. 62. A strand of sieve tubes derived from an invading hypha. A connexion has been 
established with a host sieve area and most of the walls subdividing the hypha have become bored out 
and developed as sieve areas. w = original wall of hypha in which no connecting threads or slime 
strings are found. The relations of the walls of the host and parasite in the region of junction could 
not be clearly made out; possibly the mass of blue-staining substance may represent the dissolving 
wall of the tip of the parasite hypha in a last stage of degeneration. (Ditto in Fig. 67.) x 600. 
Fig. 63. Part of a strand of sieve tubes from an old and possibly degenerating haustorium. The 
