VINCA. 



[ 808 ] 



VINE-FUNGUS. 



The villi are exceedingly vascular, and 

 form beautiful microscopic objects when 

 injected, exhibiting a network of capillaries 

 with rounded or elongate meshes. 



Fig. 803. 



Fig. 803. Two villi from a calf, without epithelium, 

 and containing each a lacteal vessel ; after treatment 

 with dilute solution of soda. Magnified 350 diameters. 



Each villus contains a lacteal, the origin 

 of which commences either in a single caecal 

 dilatation, or in a network of branches. 



The muscular fibres form a thin layer, 

 not very distinct in man, surrounding the 

 lacteals, and capable of greatly contracting 

 or shortening the villi. 



The epithelial cells are intimately con- 

 nected with each other, but easily detached 

 from the villi, often in groups or rows; 

 the free surface is longitudinally striated. 

 When acted upon by water, the cell-mem- 

 brane at the surface is separated, leaving a 

 clear space between the granular cell-con- 

 tents and the former. 



BIBL. Kolliker, Mikrosk. Anat. ii. 



VINCA, L. The generic name of the 

 garden plants called Periwinkles ; interest- 

 ing to microscopists on account of their 



striated , liber-fibres (PI. 48. fig. 30). 

 SPIRAL STRUCTURES. 



Fig. 804. 



See 



Fig. 804. Two contracted villi, from a cat. Magnified 

 60 diameters. 



VINE-FUNGUS. The vine-mildew, 

 Oidium Tuckeri, Berk., which has in recent 

 years caused such extensive destruction, has 

 formed a subject of investigation for most 

 of the principal mycologists ; and notwith- 

 standing that its natural history is not yet 

 wholly cleared up, many interesting points 

 have been discovered. As it ordinarily 

 appears, it forms a white and very delicate 

 cottony layer upon the leaves, young shoots, 

 and fruit of the vine, soon causing a pro- 

 duction of brown spots upon the green 

 structures, and subsequently a hardening 

 and a destruction of the vitality of the sur- 

 face. Under the microscope, the white 

 substance is seen to be composed of delicate 

 ramified filaments, creeping horizontally 

 over the surface, and, when the plant is 

 much developed, forming a dense interlace- 

 ment. The horizontal filaments exhibit 

 few septa, these occurring at the points of 

 branching, and they do not penetrate into 

 the interior of the epidermal layer; here 

 and there, however, they are found fixed to 

 the epidermis by a more or less developed 

 organ of attachment, consisting of a disk or 

 lobed expansion, comparable roughly to the 

 so-called root of some of the Fucoid Algae, 

 which adheres firmly to the cuticle, and 

 when removed, leaves a brownish scar be- 

 hind. The destructive effect of the Fungus 

 seems to arise from its arresting the de- 

 velopment of the epidermis, by binding its 

 structures together, and excluding the sur- 



