THE ORGANISM AND THE CELL 



15 



isecreted substance may have a firm consistency, forming with the included 

 cells a definite tissue. Such a pattei-n, which is exemplified by cartilage 

 (Fig. 8), may be termed cells in matrix. 



6. After the individual cells are formed, the}' may become entirely 

 independent free cells, as in the case of unicellular organism.s reproducing 

 by simple fission. 



The above protoplasmic growth patterns may become transformed one 

 into another as the structural development of the organism or tissue 

 proceeds. The following examples will serve as illustrations. Pattern 

 1 changes into pattern 2 in the developing endosperm of most flowering 

 })lants and the embryos of certain gymnosperms, the appearance of walls 

 throughout a multinucleate mass resulting in a multicellular tissue (Fig. 



Fig. 6. — Reticular connective tissue from 

 lymph node of cat. In the continuous cytoplasm 

 is a network of nonelastic fibers. {After M. 

 Heidenhain.) 



Fig. 7. — A colonial green alga 

 (Eudorina). The cells are contained 

 in a homogeneous envelope. (After 

 G. M. Smith.) 



108). In developing connective tissues, pattern 3 may be derived from 

 pattern 1 by the formation of large masses of fluid in the cytoplasm or 

 from pattern 2 by a loosening up of the cells. Pattern 2 may give rise to 

 l)attern 4 when the cells of undifferentiated plant tissue round up from one 

 another and form loose parenchyma. The formation of matrix character- 

 izing cartilage (pattern 5) may begin in a multinucleate mass (pattern 1 ) 

 or a multicellular mass (pattern 2). Pattern 6 develops from pattern 1 

 when a myxomycete plasmodium divides up into individual spores, or 

 from pattern 2 when spores are produced in an anther or fcin sporangium. 

 In the foregoing examples the several patterns hav(; been described as 

 arising either by a subdivision of the initial typical protoplast or by further 

 subdivision in a pattern already formed. Similar patterns sometimes 

 arise by an aggregation of free cell units or a vmion of tissue cells into a 

 continuous mass of protoplasm. Thus free cells (pattern ()) may associate 

 and form a colonial cluster (pattern 4) in certain algae. Among the slime 

 molds there is a group of species in which free cells (pattern ()) unite in 



