DEFINITION. 



n 



spots on the whole body of the Fungus or Lichen, so as to form surfaces, threads, 

 hollow structures, &c., which possess a common growth, and yet consist of sino-le 

 elementary structures developing individually (Fig. 55). 



With the exception, however, of the instances named, and of some similar 

 ones, the formation in the vegetable kingdom of multicellular bodies obeying a 

 common law of growth always arises from the cells which originate by bipartition 

 from common mother-cells remaining in connexion; the cells are in these cases 



Fig. 56.— Epidermis (e) and subjacent cortica) parenchyma 

 of the hypocotyledonary segment of the stem of the sunflower, 

 which thickens quickly after completion of germination ; the 

 darker, thicker cell-walls are the original ones, the thinner 

 transverse ones those most recently formed. The strong tan- 

 gential growth even of the epidermal cells together with their 

 cuticle is of special interest in this process. 



Fig. 55.— Part of a longitudinal section of a Gasteromycete (Crucibulum vulffare), showing the course of the hyphse : their interstices 

 are filled with a watery jelly, which has probably resulted from the conversion into mucilage of the outer cell-wall layers of the 

 hyphae. (For further details of the internal organisation, see Book II, Fungi. The drawing is partially diagrammatic, inasmuch as 

 the hyphae are shown too thick for the small magnifying of the whole (about 25), and not so numerous as in nature.) 



at least originally, so united that they appear like chambers in a mass which 

 continues to grow as a whole (Fig. 56). 



The two first-named kinds may be distinguished as false tissues from the latter or 

 true form; but there is no sharp boundary-line between them. In many cases, for 

 example, the endosperm is only in its rudimentary state a false tissue, due to the 

 coalescence of isolated cells; in its further development by cell-division it becomes 

 a true tissue {e.g. Ricinus, Sec). The cortex of many Algae and of the genus Chara 

 is formed by the coalescence of isolated filaments ; but the result cannot be distinguished 

 from true tissues. Nageli and Schwendener (Das Mikroskop, vol. II. p. 563 et teq.) may 



