r. i 



BOTANY 



filled with nuclear sap and surrounded by a membrane (w). The 

 nuclear membrane, strictly speaking, is a part of the surrounding 

 cytoplasm, and is the protoplasmic layer with which the cytoplasm 

 separates itself from the nuclear cavity. The nucleus in young cells 

 with abundant protoplasm is, as a rule, spherical. AVhen situated in 

 the lining layer of cytoplasm of older cells, it is frequently of a 



flattened form, while 



in elongated cells it 



exhibits a correspond- 



ing elongation. Ex- 



ceptionally in old 



cells the nucleus is 



forke,., lobed, or of 



some other irregular 



shape. These changes 



in form of the nucleus 



are due to slow move- 



ments, which cannot, 



as a rule, be directly 



observed. In em- 



bryonic tissues the 



nuclei are relatively 



large in proportion 



to the size of the pro- 



toplasts. Glandular 



cells are also usually 



provided with large 



nuclei. 



While the cells of the Cormophytes are 



almost always uninucleate, in the Thallo- 



phytes, on the contrary, multinucleate cells 



are by no means infrequent. In the Fungi, 



and in the Siphoneae among the Algae, they 



are the rule. The whole plant is then 



composed either of but one single multi- 



extensively 



matophores ; p. pvrenoids; 



stan-h grains. < X S40.) 



Hie. 0-2. Portions i.r two al- 

 .iacfnt cells in a hypha trnrn 



t in' stalk lit' ;w/;. 



, .Nuclei : i.. pits. 

 (X o40.) 



,,,, , 



chromic acid and stained with branched (Fig. 295), or it may consist of a 

 .aniline. n , Nuclei ; ch, ciiro- large number of multinuclear cells, forming 



,-> . m, .. , , 



together one organism. Thus, on suitable 

 treatment, several nuclei may be detected in 



the peripheral cytoplasm of each of the cells of the common fila- 



mentous fresh -water Alga Cladophora ylomerata (Fig. 6, p. 12, 



Fig. 61). 



The nuclei of the long, multinucleate cells (Fig. 62 n) of fungal 



filaments, or HYPHyE, and also of many Siphoneae, are characterised 



by their diminutive size. 



