MODERN BIOLOGY 39I 



Upon one another and lose their intermediate walls. The scientist who is 

 generally mentioned as the creator of modern plant-cytology, is, however, 

 Hugo Mohl. He was born in 1805 at Stuttgart, of a brilliantly gifted family 

 in the Government service. He became a doctor of medicine and a professor, 

 first of physiology at Berne, then — in 1835 — of botany at Tubingen, where 

 he remained until his death, in 1872.. His life was typical of the modest and 

 reserved man of science; being unmarried, he spent his days in the laboratory, 

 and his evenings, after the manner of his countrymen, at a "Stammtisch" 

 with a few friends. Even his research work has the same quiet character; 

 accurate observation of phenomena, a great capacity for placing known 

 facts in their proper light, extremely conscientious examination of his own 

 ideas, and praiseworthy consideration for those of others. He was decidedly 

 against philosophical speculations and he never produced any summary of 

 his own field of research; his writings consist of a large number of short 

 papers. The valuable results that he achieved, however, have been acknowl- 

 edged by both his own and succeeding periods. During his life he received 

 many honours, including that of being raised to the nobility with the name 

 of von Mohl, and after his death his reputation was still further enhanced. 



Mohl' s work on cell-re-production 

 Among Mohl's works should be mentioned, to begin with, his observations 

 of cell-reproduction. Before his time, and even later, opinions differed on 

 this point. He upheld clearly and convincingly that the cells in alga; and 

 even higher plants arise through partition-walls being formed between 

 previously existing cells. These partition-walls he investigated and described 

 vvtth great accuracy. We must, however, leave his and his contemporaries' 

 detailed researches in this sphere, however influential they may have been 

 in the development of vegetable anatomy; it need only be mentioned here 

 that Mohl established the cellular structure in spiral vessels, bast, bark, and 

 other components of plants, a point that had formerly been much debated. 

 Further, he carefully investigated the process of development in spores of 

 various cryptogams, finding therein both a confirmation and an extension of 

 his theory of cellular division. In another connexion we shall make reference 

 to some of his further important contributions to this subject. For the rest, 

 he was also an expert optician; a work which was unique at the time and 

 which is still worth reading was his Micrographie, a text-book on microscopy 

 and microtechnique. 



Discovery of the cell-nucleus 

 Among the investigators who contributed to the development of cell re- 

 search, which was particularly active at this period, may further be men- 

 tioned the English botanist Robert Brown, a scientist of many parts, whose 

 work will be described in another connexion. Here it need only be pointed 

 out that it was he who, in 1831, published the discovery that to the contents 



