"These illustrations were prepared from photographic prints made by the following simple method. The natural leaf was used in making an ordinary silver print, precisely as copied by a photo-engraving process. Many of these illustrations show even the delicate veins of the leaves; the tea leaf, however, is quite fleshy, and did not yield a photographic print as distinct as those from the other plants. The lower epidermis of the leaf contains most of the stomata, which are surrounded by curved cells. There are few stomata in the upper epidermis. The stomata are useful indices. Hairs are very numerous on the younger tea leaves; they always contain them. They are sometimes entirely wanting in old leaves. Dr. Thomas Taylor, in a report to the Department, mentions the presence of stone cells in tea leaves and states that his observations confirm those of Blyth in regard to the absence of these formations in certain leaves, viz., those of the willow, sloe, beech, Paraguay tea, ash, black currants, two species of hawthorn, and raspberry. After the boiling a fragment of the leaf is placed on a slide under a cover-glass and the latter is pressed down firmly with a sliding motion until the specimen is thin enough for microscopic examination. The stone cells are valuable aids in the microscopical study.

In the general study of the serration and venation of a tea leaf the specimen should be steeped in hot water, and, after softening, the leaves should be unrolled and spread upon a glass plate for examination by transmitted light. Even small fragments of tea leaves will usually show some distinctive characteristic.

1 Bulletin No. 13, Division of Chemistry, Part 7, Plates 39 and 40.

In general it may be stated that a microscopic examination is only necessary in exceptional cases. In doubtful samples the stomata should be examined, and a search should be made for stone cells; the epidermis of both the upper and lower leaf should be examined. Even in the case of dust the microscope will furnish conclusive evidence as to whether it is from tea or some other plant."