1890.] MICROSCOPICAL JOURNAL. 229 



parts ma\^ be located, one has either to take the chances on getting the 

 sections in the right plane, or open the coats enough to see how the 

 parts are arranged and then mark the seed in some way. Having se- 

 lected a well-filled seed, I next put them in water at the ordinary tem- 

 perature of the laboratory from 24 to 36 hours. From the water they 

 are transferred to weak alcohol (40 per cent.) and gradually hardened 

 by transferring to stronger until they are in 95 per cent, alcohol. 

 Schultze's apparatus may be used to advantage in hardening. Next 

 transfer to equal parts of alcohol and chloroform for from 4 to 8 hours, 

 the time depending on the size of the seeds. Then in pure chloroform 

 for the same length of time. Then for 34 hours into chloroform with 

 as much paraffin in it as it will dissolve at the ordinary temperature. 

 From this into paratiin softened with chloroform, the melting point of 

 which is about 36'^ C. The specimens are kept in this melted paraffin 

 34 hours. I have alwavs been careful not to let the temperature go 

 above 47° C, although I think it probable that a somewhat higher 

 temperature would not injure the tissue of a seed. From this the seed 

 ma\' be imbedded in hard paraffin and will be found to be thoroughly 

 infiltrated. 



The seeds mavbe sectioned in the paraffin blocks either free-hand or 

 with a microtome. It is highly essential that the sections be kept in 

 series and that none be missing. The texture of a seed is so fragile 

 that when cut in thin sections the least carelessness may spoil a section. 

 A very efiectual wav to keep sections intact when they are cut in 

 paraffin is that proposed by Dr. Mark (^American Nai.^ 1SS5, p. 638). 

 It consists in collodionizing the object as the sections are taken. Very 

 thin collodion should be used and applied to the cut surface after the 

 section is taken. Lee ('' Vade Meciiin^''' 3d edit., p. 150) recom- 

 mends that '' the collodion be of such a consistency that when applied 

 to a surface of paraffin it dries in two or three seconds. This has no 

 tendency to cause the sections to roll. * * * As soon as the collo- 

 dion is dry, which ought to be in two or three seconds, cut the section, 

 withdraw the knife, and pass the collodionized brush over the newly 

 exposed surface of paraffin." The section is placed collodion side 

 down on the slide. They may be fastened by first painting the slide 

 with a few drops of clove-oil collodion, placing them in it, and then 

 evaporating ofithe clove oil. 



The sections are then placed in xylol for 15 minutes. This removes 

 the paraffin. They are then washed in alcohol, afterwards with water, 

 and stained. I have found no stain that was as efi'ective in staining 

 seeds as hcEmatoxylin. They should be stained from 3 to 5 minutes. 

 After washing the staining agent away with water, dehydrate with al- 

 cohol, and clear. Three parts of turpentine and two parts of carbolic 

 acid make a very good clearing mixture. Canada balsam dissolved 

 in xylol is used for mounting. In sections thus prepared one can dis- 

 tinguish without difficulty in Shepherd's Purse, Goldenrod, or any en- 

 dospermous seed, the coats, the plumule composed, as is the lower tip 

 of the radicle, of small thin-walled nucleus-bearing cells. These two 

 regions of growth are connected by slightly elongated cells which are 

 also thin-walled. The larger cells making up tlie tissue of the coty- 

 ledons are stored with food. In many seeds a trace of a fibro-vascular 

 system may be seen ; also the peculiar arrangement and markings of 

 the cells composing the coats. 



