122 VEGETABLE CELLS. 



dary cell. The appearances are the same here as in the 

 parietal cell-formation of the Algse. From this indubitable 

 example we have numberless intermediate stages to those 

 cases in which no evidence is afforded, either for or 

 against. The succession of states and the transitions 

 show, however, that the same explanation must come into 

 application for all cases. 



The conclusion that all vegetative cell-formation is 

 parietal, is also supported by analogy. The parietal cell- 

 formation of Algae and special parent-cells occurs, as a 

 rule, with central nuclei. But to this rule there are some 

 exceptions, when the parietally originating cells possess a 

 lateral nucleus.* In the vegetative cell-formation of the 

 higher Cryptogamia and the Phanerogamia, the nucleus 

 is, as a rule, lateral ; yet it appears to me that, in ex- 

 ceptional cases, it may be free also. The appearances in 

 the Algse and special parent-cells on the one hand, and in 

 the cells of other plants on the other, are essentially the 

 same, only they present themselves much more dis- 

 tinctly in the first, and much more definitely require to 

 be explained as parietal cell-formation. 



Parietal and free cell-formation would, according to my 

 views, extend through the vegetable kingdom within the 

 following bounds : 



Parietal : the vegetative cell-formation of all plants, 

 further, the reproductive cell-formation of many Alga and 

 Fangi. Free : the reproductive cell-formation of most 

 (not all) plants, namely, the germ-celt, formation of many 

 Fungi, many Algce, and of the Lichens ; the formation of 

 the spores inside the special parent-cells in the four-spored 

 Cryptogamia (?), the formation of the pollen-cells inside the 

 special parent-cells in the Phanerogamia (/*), and the forma- 

 tion of the endosperm-cells in the Phanerogamia. 



The cells which have originated by parietal cell-forma- 

 tion possess central nuclei (in most Algae, and generally 

 the special parent- cells), or lateral nuclei (in most Fungi, 



* Part I, Hay Trans., p. 552 ct scq. 



