IV 



has left his most indelible mark in botanical science. In 1841 he 

 showed once for all that the Polypiers calciferes of Lamonroux were 

 not merely Algce, but that the affinities of the diverse types which they 

 comprised could be determined with some certainty. This conclusion 

 was not a happy guess, but was based on a laborious examination of 

 the whole class of Algce with the object of arranging their chaotic 

 assemblage on a basis approaching as nearly as possible to a natural 

 classification. The results were given in an elaborate paper, published 

 in 1842. The divisions proposed are not essentially very different 

 from those which are generally accepted at the present day ; and they 

 were really more natural than the subsequent but far more artificial 

 classification proposed by Harvey, which has long held its ground in 

 this country. 



In this particular line Decaisne himself, owing probably to the 

 distraction of his energy by official duties, did little more. Not- 

 withstanding this, he must always be regarded as the founder of 

 the French school of Algology, the literature of which is the basis 

 of our present knowledge of this branch of vegetable morphology. 

 In 1839 Thnret came to Paris, and received from Decaisne instruc- 

 tion in the rudiments of botany. Decaisne and Thuret began to work 

 together on the reproduction of Fucus, which they procured from the 

 fish-market of Paris. They soon found it, however, necessary to visit 

 the coast to carry on their observations, the results of which were 

 published in 1844 in a joint paper in which they first accurately 

 described the antherozoids, assigning to them their true function, and 

 gave an account in some of the species of the beautiful process of the 

 division of the primary oosphere. After Decaisne's appointment to the 

 Direction of the Jardin des Plantes, Thuret carried on his algological 

 work for a time alone, ultimately associating himself with Dr. Bornet, 

 who is happily still living, and occupied with the gradual publication 

 p. of their joint and classical work. 



In 1858 Decaisne began the publication of " Le Jardin Fruitier du 

 Museum," which was only brought to completion within a few years 

 of his death. This in form is one of the most sumptuous of modern 

 botanical books ; in matter it is a monument of patient labour on the 

 cultivated forms of fruit-plants, elaborated in the thorough spirit of 

 the naturalist ; its value in a scientific sense will gain with time when 

 the races figured and described in it are supplanted and lost. Students 

 in the future will turn to Decaisne's minute and laborious pages to 

 compare the phases of variation which he has permanently recorded. 

 In much other work of this kind he had the collaboration of his 

 friend Naudin, now director of the botanical station at Thuret's 

 country seat at Antibes, which the heirs of the latter presented to 

 the French Government. 



Decaisne did not, however, by any means devote all his energy to 



