118 Brenchley . — On the Strength and Development of 
Material was examined which had been collected during the summer 
of 1904, killed and fixed in acetic alcohol. This consisted of samples of 
a typical English wheat, Square Head’s Master, taken from two plots in the 
Broadbalk Field, Rothamsted, one of which has received no manure what- 
ever since 1843, while the other has yearly a very heavy dressing of nitro- 
genous manure in the form of ammonium salts ; the other samples were 
Red Fife, a typical strong Canadian wheat, and a Hungarian wheat, very 
strong when grown in Hungary, both grown at Rothamsted. The grains 
were collected at irregular intervals between July 21 and August 30, note 
being made of the dates of cutting and carting the corn. 
When the examination of the material was begun, a great deal of 
difficulty was experienced in securing the permeation of the grains by 
paraffin wax, preparatory to sectioning with the microtome. The pericarp 
of the caryopsis is very tough, and offers a decided obstacle to penetration 
by such a heavy liquid as melted paraffin wax. Various clearing media 
were tried — xylol, bergamot oil, paraffin, and cedar wood oil — but it was 
ultimately found best to cut the grains in half, transfer into the paraffin 
wax by way of bergamot oil, and then to let them soak in several changes 
of wax for one to four weeks previous to embedding, according to the age 
of the grain. Attempts were made to hasten penetration by placing the 
material under the action of a suction-pump, the tube being led into the 
embedding oven for the purpose; but no great measure of success attended 
the experiment. 
After sectioning, numerous trials were made with various stains and 
double stains. It was found that the best results were obtained by over- 
staining for several hours (five or more) in very dilute Delafield’s haema- 
toxylin, then, after washing with tap-water, dipping the slide for a few 
seconds into acid alcohol (5 drops HC1. to 100 cc. of 70 per cent, alcohol), 
finally placing in tap- water till the sections turned blue again. After a light 
double-staining in orange G, the series were dehydrated, cleared in clove 
oil and xylol, and mounted up in Canada balsam. At a later stage of the 
investigation, considerable use was made of Heidenhain’s iron haemato- 
xylin, which gave excellent differentiation when carefully controlled. With 
this stain the sections were mordanted with the iron alum, and then allowed 
to remain in the 0*5 per cent, haematoxylin overnight. It was found 
easier to control the final differentiation by the ferric alum after a long 
immersion in haematoxylin. 
In addition to the microtome series a good deal of sectioning was done 
by the aid of a Leitz hand-microtome. The ordinary elder pith proved 
useless for holding such a large and elastic object as a wheat grain, so after 
various trials it was found that the pith from lime twigs answered the 
purpose admirably, as it was firm enough to withstand the considerable 
amount of pressure put upon it, while it was not difficult to cut. These 
