68o 
T/today.—On the Histological Relations between 
Fig. 26. Part of an old transverse sieve plate from the main stem of same, showing the callus 
change extending to the wall between the rods, x 1,500. 
Fig. 27. Lateral plate from sieve tube of C. europaea (preserved in October), showing accumu¬ 
lation of callus, x 750. 
Fig. 28. C. rejlexa. A and b = sieve tubes of two separate groups, separated by parenchyma 
and connected by transverse connexion D. The longitudinal wall of A is traversed by numerous 
groups of minute callus rods, x 500. 
Fig. 29. Surface view of longitudinal wall of sieve plate of C. rejlexa , showing groups of con¬ 
necting threads, some of which are beginning to be bored out. x 600. 
Fig. 30. Surface view of sieve field on longitudinal wall of sieve tube of C. europaea. The 
slime strings are arranged in little groups, and each string is enclosed in a minute callus rod 
(shown in Fig. 30 a), x 600. 
Figs. 31 A and B. Stages in development of the lateral sieve fields {C. reflcxa) seen in section, 
x 1,000. 
Fig. 32. Longitudinal wall of a mature sieve tube of C. rejlexa , showing well-marked pits, each 
traversed by a group of slime strings. Median nodules well defined, x 1,500. 
Fig. 33. Ditto, showing a larger sieve field, x 1,000. 
Fig. 34. Single pit more highly magnified. 
Fig. 35. Longitudinal wall from sieve tube of C. europaea (preserved in October), showing 
accumulation of callus over each pit. x 500. 
Fig. 36. Surface view of lateral sieve fields in C. reflexa , showing spread of callus change, 
x 500. 
Fig- 37 - Ditto, smaller fields and callus change further advanced, x 500. 
Fig. 38. Ditto, showing large accumulation of callus over the ends of the small sieve fields, 
x 500. 
Fig. 39. Longitudinal section of sieve field from a sieve tube of C. europaea (preserved in 
October), showing remarkably large median nodules and considerable accumulation of callus, 
x 1,000. 
Fig. 40. Longitudinal wall of sieve tube of C. rejlexa in section, showing large accumulation of 
callus on the sieve-tube side of the wall. ‘ Paths’ through callus, x 1,000. 
Fig. 41. Wall between sieve tube and companion cell (C. rejlexa ), showing callus change on 
sieve-tube side of wall only, x 1,000. 
Fig. 42. Ditto, C. europaea (October), x 800. 
Fig. 43. Short element of sieve tube from haustorium of C. rejlexa. Each thread has its own 
callus rod; at c a small accumulation of callus has taken place. (Greatest length of cell *= 64-4 n ; 
A-B = 11-2 /x; the group A consists of eleven threads ; the group b of sixteen.) x 500. 
Fig. 44. Short element from haustorium of C. rejlexa , showing accumulations of callus, 
x 1,000. 
Fig. 45. An exceptionally large mass of callus in old haustorium, nearly filling cell, x 1,000. 
Relation oj Host and Parasite. 
Fig. 46 A. Tip of invading hyphal cell from haustorium of C. europaea , making its way through 
the cortex of Vitis. It has already two large nuclei, x 800. 
Fig. 46 B. A similar cell of C. rejlexa , passing through the longitudinal wall of a cortical cell 
of Salvia and boring a clean hole in it. At the edges of the hole the two walls are fused together, 
x 500. 
Fig. 47. (Figs. 47, 48, 49, 51 from C. europaea on Vitis.) An invading hyphal cell which has 
nearly reached the host phloem and is four-nucleate. x 800. 
Fig. 48. An invading hypha which has reached the phloem of the host. The large size of the 
nucleus is apparent from a comparison with the dimensions of the transverse section of a host sieve 
tube, x 800. 
Fig. 49. Transverse section of an invading element, which has reached the phloem, taken at 
some distance from the tip. Longitudinal divisions have taken place to form a strand, and the thin 
longitudinal walls (/) are seen to be packed with connecting threads, x 1,000. 
Fig. 50. Two invading cells of C. rejlexa , near host phloem. The right-hand element has just 
bored through a host element; its compiessed shape may be taken as an indication of the softness 
