32 II. FOOD RESERVES IN SITU. 



The preparation must now be labelled, preferably at both ends 

 of the glass-slide. This may be done with gummed squares of 

 paper, upon which must be written at least the name of the 

 plant, the nature of the object, the direction of the section, if 

 it be one, the medium in which it is preserved, any staining 

 material used, and the date. A preferable method, however, is to 

 use thin cardboard labels, made, for example, from Goodall's thin 

 Bristol boards, and in size about the breadth of the glass-slide by 

 about f or J inch. These can be cemented on to the slide by 

 means of any one of the numerous forms of glass- cement, such as 

 coaguline, mend-all, etc. A quantity of slides can be prepared 

 at one time. The card-labels are cemented on both ends of the 

 slide, and these are tied into bundles to dry under pressure. 

 This method is very economical for keeping preparations, as 

 all those of a similar kind can be tied into a bundle, with 

 a plain slide over the uppermost, through which its label will 

 be visible. Preparations preserved in glycerine do not then 

 necessarily need to be closed with Canada balsam, provided the 

 preparation is thin, so that little glycerine is used. If it is 

 necessary to fasten card-labels with gum, it is best to cover each 

 end of the slide first with a strip of gummed paper, the ends of 

 which should overlap under the slide, and fasten the card-label on 

 these ; otherwise the label would readily spring away from the 

 slide. The card can be fastened direct upon glass, without danger 

 of " springing," if a solution be used composed of 100 grams of 

 gum-arabic in 250 c.c. of water, to which is added a solution of 2 

 grams crystallised aluminium sulphate in 20 c.c. water. 



If it be desired to approximately mark the position of a very 

 minute object in a preparation, or of a special one amongst 

 several sections upon the same slide, this may be done by draw- 

 ing a circle (with Indian ink or a Faber's special pencil) upon the 

 cover-glass, surrounding the position of the object. 



Aleurone Grains of LupiniCs. Let us now take the seed of the 

 white Lupine (Lupinus albus), or other allied species. Once 

 more halve the seed across, and take sections from the moist- 

 ened cut surface. Sections observed in water show in the cells 

 rounded aleurone grains with vacuoles. In order to see the 

 grains in their natural form they must be observed in glycerine. 

 The grains then appear at first refractive, angular, gradually 

 showing in their interior a fine network, granular. Lying closely 

 together they fill up the cell ; a small quantity of ground sub- 



