Chap, v.] CONSTITUTION OF ORGANISED BODIES. 45 



appears ; but in the ease where the fusion of the elements has 

 been less complete, the vessel remains nodose, being fashioned in 

 the likeness of a chapelet.' It is then called utriculous. Some- 

 times, instead of being juxtaposed in linear series, the formative 

 cells assiume the shape of a vascular network. 



According to M. Ch. Robin,^ we are able in vegetal tissues to 

 distinguish as clearly as in animal tissues a small number of 

 histological types. These types have as origin a cell ; but from 

 their advent they bear a distinct physiognomy, and they are 

 never seen undergoing or accomplishing mutual transformation. 



The first of these types is that of cells properly so called, 

 offering moreover a certain number of varieties according as 

 they are spheroidal, ovoidal, fibroidal, stellated, or cyliadroidal. 

 It would be needful to range in this class the cells of the 

 epidermis of plants, those of the cork-tree, of cambium, and of 

 marrow. We might naturally add the monocellular plants, such 

 as the red utricles which sometimes give a red tinge to the snow 

 of the Alps (^protococcus nivalis of Saussure), and the diatomous 

 plants. The second type is that of the filamentovx cells, all 

 more or less cylindrical, and eight or ten times longer than -^ey 

 are broad. We may cite as an example of filamentous tissues 

 the cells forming the mycelium of the cryptogams, and also 

 certain monocellidar infusoria, such as the bacteria and the 

 vibrionp, if indeed we admit that botany can claim as belonging 

 to its domain these dubiously-defined organisms. 



Every plant solely composed of the two histological types 

 spoken of above, is a cellular plant. 



The fibrous cells represent the third type. These are they 

 which, juxtaposed lineally, form the ligneous fibres of wood and 

 of liber. 



Finally, the vascular cells form the fourth ij^. These are 

 they which by their linear juxtaposition and the partial reab- 

 sorption of their walls, constitute canalicules — vessels. To the 



' In the sense of rosary or string of heads. — Translator. 

 ' Aliments Anatomiques. 



