BOTANY. 3' 



as the spores of certain aquatic plants, may have cilias or fine hairs, by 

 means of which they can execute a progressive motion through the water. 

 Under such circumstances, they have often been considered and described 

 as infusorial animalcula. 



Pitted Tissue {Bothrenchyma) is a modification of cellular tissue caused 

 by the unequal deposit of the thickening matter in the Avail of the cell. 

 leaving thinner portions, -which, when viewed by transmitted light, appear 

 like pores or pits. A spiral thread or fibre is sometimes found coiled up in 

 the inside of the true cell wall, which, when the latter is dissolved, uncoils 

 and exhibits itself in its true character. Such cells, called spiral cells 

 {Tncnchi/ma), are frecpient in the orchidaceous and cactaceous plants. This 

 fibre varies froui ^zöö to toIöö of an inch in diameter, and is solid, with a 

 cross-section of various shape. The coils of the spire are sometimes 

 broken up and recombined in various ways, so as to appear as rings, 

 reticulations, bars, or dots, thus producing aniudar, reticulated^ scalar i form., 

 or dotted cells. 



Cells are sometimes aggregated so closely together as to leave no visible 

 interspaces, the tissue being then termed perfect Parenchyma. Imperfect 

 Parenchyma is Avhere the cells touch at certain points only, leaving intervals, 

 which, when regular and continuous, are called intercellular passages or 

 canals : when irregular and limited, intercellular spaces or hacunm. A 

 division of cellular tissue is sometimes made into Parenchyma., where the 

 cells fit together by plane faces, as in the pith and outer bark, and 

 Prosenchyma., where the cells are fusiform, this being confined to the inner 

 bark and wood. The mode in which the combination of cells is efiected, 

 varies under different circumstances ; sometimes they are simply approxi- 

 mated and fused together, sometimes united by an intercellular matter which, 

 in sea weeds, forms a considerable part of the bulli of the plant. 



The external investment of the cell is composed of an unazotized 

 primary matter, termed cellulose. This is lined by an originally mucilaginous 

 matter containing nitrogen, called Protoplasm,, and inside of this is the 

 Cytoblastema. A w^eak solution of iodine applied to the young cell causes 

 the protoplasm to turn brown and leave the cellulose. The tissue is further 

 modified by the addition of various matters, the most important of which is 

 Sclerogen or Lignine applied on the inside, the substance to Avhich wood 

 owes its hardness. This consists of C35, H24, OK), and may be dissolved 

 by hot nitric acid. In all cell deposits there is a more or less tendency to a 

 spiral arrangement. 



Each cell will be found to contain, at one perod of its existence, a small 

 body called a nucleus, this often embracing one or two minute dots called 

 nucleoli. This nucleus may either lie free in the cell, or be attached by 

 threads, or fastened directly to the cell wall. Some recent authorities of 

 great weight, however, deny the existence of a primordial nucleus in every 

 cell. 



In addition to the carbon, oxygen, hydrogen, and nitrogen, found 

 universally as the constituents of the cell, there are other materials more 

 variable in their appearance and amount, as Sulphnr, Phosphorus, Potash, 



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