STRUCTURE.] PHYTOZOA. 19 



most common direction is spiral. Whether it is solid or hol- 

 low has been disputed ; Purkinje asserts that it is hollow, but 

 there can be no doubt that it is really solid, as it is believed 

 to be by the best anatomists, and as its mode of formation 

 indicates. Elementary fibre has a constant tendency to ana- 

 stomose, in consequence of which reticulated appearances are 

 frequently found in tissue. Slack adds that it sometimes 

 branches. Like membrane it is increased in thickness by 

 the deposit of sedimentary matter on that part which does 

 not adhere to the membrane, as has been proved by some 

 beautiful microscopico-chemical experiments of Schleiden. 



In its most simple state the elementary fibre forms a loose 

 spire coiled up in the interior of cells, with a thickening at 

 one end derived, according to the opinion of Nageli, from a 

 nucleolus (see postea), tapering to a point at the other, having 

 an active vermicular motion when extricated from the cell in 

 water, and losing the motion at the instant when it is acted 

 upon by iodine. Such loose spires are common in the anthe- 

 ridia of mosses and liverworts where they were first noticed ; 

 they have since been found in the young leaves of ferns and 

 elsewhere. The early observers of them supposed them to be 

 animalcules analogous to the genus Vibrio ; and Grisebach, 

 who took this view of their nature, called them phytozoa, and 

 detected them elsewhere, giving the following account of 

 them. (See Annals of Natural History, vol. xv. p. 265.) 



" The occurrence of phytozoa in organs of vegetation, led 

 me to expect that they might be detected in PhaBnogamous 

 plants. I had frequently observed in the water on the glass 

 stage, while examining leaf-buds, masses of dark particles, 

 which, on being magnified 200 times, exhibited a lively 

 vermicular motion. On recently re-examining them in the 

 buds of Rhamnus infectorius and pumilus, I saw distinctly, 

 with a magnifying power of 410, that they were phytozoa, 

 accurately agreeing with those in ferns. Like them they 

 consist of long-tailed globules which are individually inclosed 

 in a very minute spherical cell, or swim freely about in the 

 water, oscillate in a lively manner, and sometimes move their 

 tail." 



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