57 



the standpoint of the time. Ivleyen no longer shares Unger's view that the 

 parasites as excrement-organisms are the product of a formative development 

 latent in each plant, the disease occurring in a more or less developed form 

 and state of independence according to the constitution and strength of the 

 host-organism. On the contrary, his Plant-Pathology, in the discussion of 

 smut fungi, emphasizes especially that "observations on the production of 

 the smut show most clearly that we have to do here with true entophytes : 

 we will find that some smut species are shown as particular parasitic growths 

 in the interior of the cells of the plants attacked by them and that the smut 

 mass is not to be compared with animal pus." 



The whole title of Meyen's "Plant Pathology" really reads : — "Hand- 

 buch der Pflanzenpathologie und Pflanzenteratologie" edited by Dr. Chr. 

 Gottfr. Nees v. Esenbeck. Vol. I. "Plant Pathology." According to this, 

 a second part. Teratology, was to be expected. j\Ieyen himself intended to 

 work up such a volume, but, according to the Editor, left no material for it. 

 Just as Nees v. Esenbeck was about to undertake this himself, there appeared 

 tlie "Elements de Teratologic vegetale, au Histoire abregee des anomalies de 

 I'organisation dans les vegetaux; par A. Moquin Tandon, Doct. scienc. et 

 med. etc., director du jardin des plantes de Toulouse. Paris 1841." C. F. 

 Jaeger "Ueber die Missbildungen der Gewachse" (1S14) and Thomas Hop- 

 kirk. "Flora Anomala" (1817) should be mentioned as forerunners of this 

 work. We learn from the German translation of Moquin Tandon's^ book, 

 that the translator, C. Schauer, was able, as specialist, to call attention to 

 many misunderstandings and errors made by the author, especially in the 

 German citations and to make additions from his own observations. Moquin 

 Tandon says, "By the expression 'malformations', 'monstrosities' (monstra) 

 is generally understood innate, more or less important and complicated vari- 

 ations from the type of a species, which are disfigurations and oppose the 

 regular course of a functioning by hindering or arresting it." We are better 

 satisfied by de CandoUe's definition (Theor. element. I. ed. p. 406), by which 

 monstrosity is any disturbance in the economy of a plant, which is followed 

 by a change in organic form and arises from an internal disposition, almost 

 never from a visible cause. Moquin Tandon's book is still indispensible to 

 every specialist because of its admirable bibliographical references. 



About this time, the science of infectious diseases received a new im- 

 petus because of the rapid spread of the potato disease which is still worthy 

 of especial attention. It is one of the most dreaded enemies of agriculture, 

 and is described in the text books as potato Phytophthora rot. We owe one 

 of the first publications on this subject to Martius- and from that 



1 Pflanzenteratologie. Lehre von dem regelwidrigen Waehsen und Hilden der 

 Pflanzen. By A. Moquin Tandon. Translated and supplemented by Dr. .J. C. 

 Schauer. Berlin 1842. 



2 Die Kartoffelepidemie der letzten .Jahre. Mtinchen 1842. 



