FOKM OF THE PLANT-CELL. 35 



part of their layer obscures observation, and where from other causes it 

 has been found impossible to make complete observations. Nevertheless, 

 I have seen very generally, especially after the use of nitric acid, by 

 which the cells are separated from one another, sometimes two cells, with 

 their cytoblasts in a single cell in Gasteria nitida, and in the terminal 

 buds of Cypripedium Calceolus, and in the spongioles of the last plant, 

 and of Neottia Nidus avis two cytoblasts loose in a single cell, and 

 near by two cells with cytoblasts enclosed in another cell. All young 

 cellular tissue in the Phanerogamia, without exception, exhibits the 

 cytoblast. In the development of the pollen, the cells are seen filled 

 with a thick grumous fluid, which separates into four parts, around each 

 of which there is suddenly developed a tolerably thick membrane. These 

 might be regarded as four large cytoblasts, if the appearance of the 

 membrane was not attended with another characteristic cytoblast. But 

 I have observed in Passiflora Princeps and Cucurbita Pepo, at the 

 time when the dark mass in the primitive cell was yet undivided, a 

 number of clear cells, each with a little clear cytoblast enveloped in this 

 dark mass. May not these be the pollen cells, which gradually form 

 within, take up the grumous matter, and, again precipitating it gradually 

 in their cavity, grow thereby, and, suddenly dividing into four parts, 

 become visible ? I have not made any observations on the intermediate 

 stages, and Nageli (in the paper before quoted) thinks he has observed 

 another process. I have, however, found some interesting facts in 

 Rhipsalis salicornioides, which I have not had an opportunity to follow up. 



Inferences from the above Facts. Up to the present time no fact 

 has occurred which is not in accordance with the complete precedence of 

 the cytoblast, as above observed. The indications of its precedence are 

 only obscure and incomplete in those cases in which accurate observa- 

 tion is surrounded by insurmountable obstacles. It is in the formation 

 of the spores, the foundation of the future plant, in Cryptogamia ; in 

 the embryo, the young plant itself, of the Phanerogamia, that the pre- 

 cedence of the cytoblast is fully made out. Both serve as points of sup- 

 port for analogous conclusions in other cases ; and it appears, until further 

 researches may necessitate modification, that we may safely conclude 

 that the precedence of the cytoblast in the formation of cells is a 

 universal fact. 



If, further, we regard the easy transformation of the assimilated 

 matters, and may from artificially conducted experiments draw the con- 

 clusion that the nitrogenous matter which I have called mucus, and 

 which forms the cytoblast, is the substance whieh calls forth these 

 transformations, and if we further remark that sugar and dextrin are 

 more easily soluble than jelly, and that sugar and gum are changed into 

 jelly if the quantity of water is not increased, and which must be 

 necessarily precipitated, we must regard the whole process of cell- 

 formation as simply a chemical act. The gathering together of granules 

 of mucus to form the cytoblast we can as little explain as that, when we 

 form a solution of two salts, if we throw into the mixture a crystal of 

 one or the other salt, that salt alone crystallises around it. 



Analogies. Schwann has pointed out, in an acute and profound 

 treatise*, that the animal organism also is composed of cells, and that 



* Microscopic Researches on the Analogy in the Structure and Growth of Animals 

 and Plants. Berlin, 1839. Although in this work the analogies between the formation 

 of vegetable and animal tissues are pointed out, it should be borne in mind that there 

 are some tissues which are peculiarly animal, and which constitute the distinction be- 

 tween the plant and animal. Some of the animal tissues, such as the cell and nucleus 



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