556 Obituary. 



the striae, making great use of photomicrography, which in Italy 

 had already been employed by the Abbe Castracane as early as 

 1862. As an object for photomicrographic study, he made special 

 use of Amphipleura pellucida, determining exactly the number of 

 strise, which differs very little from the number already determined 

 by Castracane. 



By the accumulation of observed facts, aided by the possession 

 of a rich collection of slides, H. van Heurck arrived at a profound 

 knowledge of the siliceous Algse, with the aid of his illustrious 

 friend Albert Grunow, who, in the words of van Heurck himself, 

 " elucidant les cas difficiles, et, nous faisant part de dessins originaux 

 si exact," facilitated, with Mr. Fr. Kitton, the editing of the well 

 known Synopsis des Diatomees de Belgique, a work absolutely 

 indispensable to botanists who would give themselves up to the 

 study of the Diatomacese.* 



But when the Synopsis became out of print, H. van Heurck 

 conceived the idea of giving to science a work more accessible to 

 the common run of diatomophils, containing descriptions and 

 figures of all the species found in the North Sea and the countries 

 surrounding it, that is to say, Great Britain, the extreme north of 

 France, Belgium, Holland, Denmark, Norway. This idea took 

 shape in The Treatise on the Diatoniacese, first published (1896) 

 in English under the editorship of W. E. Baxter, the skilled 

 diatomist, who undertook not only the translation of the text but 

 also all the cost of printing the English edition, of which he was 

 to some extent the inspirer. In 1899 the same book was pub- 

 lished in French (Traite des Diatomees) by van Heurck himself, f 



The diatomologist finds in this important treatise valuable 

 information on the morphology and biology of diatoms, on the 

 mode of collecting, studying, and preparing the material, but 

 particularly a section devoted to descriptive and systematic work, 

 for which van Heurck has followed in his main plan the classifi- 

 cation proposed by Hamilton L. Smith (1872) in the micrographic 

 journal The Lens of Chicago. 



The great Treatise, with 35 plates and numerous figures in the 

 text, contains also some novelties,, among which may be cited 

 Beicheltia, a new genus allied to Brebissonia and Berkeley a ; 

 Grunowiella, a new genus created for Sceptroneis gemmata Grun. 

 and S. marina (Greg.) Grun. ; Muelleriella, a new genus of 

 Melosirese founded on Pyxidicula limbata Ehrb. ; Helminthopsis, 

 Butilariopsis, and Baxteria, new "genera belonging to the Bid- 

 dulphise. 



During the last few years van Heurck applied himself to the 

 compilation of an algological florule of the Channel Islands (Pro- 

 drome de la Flore des Algues Marines des lies Anglo-Normandes, 



* Compare Delogne in Bull. Soc. Belg. Micr. xii. (1885-6) pp. 72-3. 



t Compare the account given in Bull. Soc. Belg. Micr. xxv. (1898-9) pp. 25-6. 



