ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 73 



observed ; the splitting occurs at somewhat distant points in a filament, 

 though in favourable circumstances a minor proportion of the filaments 

 become divided into few-celled fragments. It is suggested that splitting 

 is due to the effects of renewed turgor on desiccated filaments 

 in which degeneration of the cuticle or a weakening, due to the 

 development of mucilage between the two lamellae of the septa, has 

 taken place. (2) The production of aplanospores occurs in all seasons 

 of the year, but is dependent on an ample supply of water. Cells that 

 give rise to aplanospores usually contain an abundance of a special 

 substance and also granules. A white refractive substance is described ; 

 it appears in the cells under certain conditions in the form of 

 granules and rounded masses. It arises chiefly in the region of the 

 polar vacuoles, but also sparsely distributed in the peripheral proto- 

 plasm. Two conditions favour its production, viz. drought, and a 

 plentiful supply of carbohydrates, e.g. glucose. It appears to be 

 associated with a second special substance (referred to above), and 

 possibly is formed as a result of concentration of this substance. Since, 

 in suitable circumstances, the cells ai'e capable of eventually absorbing the 

 granules, these evidently serve as a food-store. During the first weeks 

 of a period of drought the death-rate decreases, while the abundance of 

 granules increases to a maxiinum. When growing in its native habitat, 

 this alga in all probability rarely passes beyond this first stage of 

 desiccation, as the spells of dry weather in temperate regions are 

 comparatively short, and dew is continually deposited, especially in 

 summer when the drought is most extreme. 



Staining of Minute Algae.'' — J. Ben Hill describes a satisfactory 

 method of manipulating microscopic organisms in staining, to prevent 

 the loss of such minute objects as SphsereJla, Pandorina, VolvoXy 

 Pediastriim, and the Desmideee. From the killing solution the material 

 is transferred to a filter, and there washed with distilled water from a 

 wash-bottle. It is then treated withO'l p.c. iron-alum solution, and 

 washed as before; then stained cautiously with O'l p.c. aqueous 

 haematoxylin, and thoroughly washed as before. The stain is carefully 

 differentiated with 0"1 p.c. iron-alum solution; and once more a 

 thorough washing with distilled water from the wash-bottle follows. 

 Then the filter-paper is punctured, and the material is dehydrated in an 

 open vessel with glycerin, followed by washing on a filter with 95 p.c. 

 and absolute alcohol. The material is then quickly transferred to 

 10 p.c. Venetian turpentine for concentration and mounting. 



Pleodorina illinoiensis.f — ^X. B. Grove publishes a supplementary- 

 note on Pleodorina ilUnolensis, which he recorded as occurring in cart- 

 ruts at Harborne, Warwickshire, in the spring of 1915. He found it 

 in the same place in 1916 and 1917 ; but in April 1917 it was in larger 

 quantity, and associated with equal quantities of Pandorina Morinn and 

 Eudorina elegans, and with other Algae. And, though the elliptical 



* Bot. Gaz., Ixiii. (1917) pp. 410-12. 

 t New Phytologist, xvi. (1917) p. 180. 



