CURRENT LITERATURE. 141
straight or curved rods, also of varying length and thickness. Both kinds multiply by transverse division. Passing from the meristera to the older cells of the root, some of the larger rods begin to grow, and enlarge at one or more points, and finally become plastids with starch grains in the enlarge- ments ; those that do not become plastids at length disorganize. The minute rods and granules persist practically without change in size, form, and number as the cells grow older. He calls the larger rods " primordia ot plastids", and restricts the term chondriosomes to the minut#bodies.
Zea mays, Adianttm, Pinus seeding, and Elodea. gave similar results. In Marchantia both plastids and their primordia are present in all vegetative cells, but chloroplasts are early eliminated from spermatogenous tissues and only the chondriosomes remain. It bas been suggested that chondrio- somes are the remains of disintegrated plastids. Anthoceros furnishes valuable evidence on this point, since each cell contains but one chloroplast. The author finds chondriosomes present in large numbers in all cells; they are just as numerous in cells with healthy normal chloroplasts as in those in which the chloroplasts appsar abnormal. This disposes of the plastid origin of chondriosomes.
The conclusion is that chondriosomes and the primordia of plastids are quite distinct, and are fairly easily distinguished by their difference in size, even though they show the same staining reactions. Much of the confusion in earlier writings has been due to failure to recognize this fact. He thinks "We are now justified in the view that leucoplasts, chloroplasts, and chondrio- somes are organs of the cells, of the same rank as the nucleus ", and that if this be true, " these bodies must be transmitted from individual to individual in the form of their primordia, and that chromatin is not the sole carrier of hereditary characteristics". "To claim that certain phenomena of fluctuat- ing variability and other numerous characteristics, Mendelian or otherwise, owe their appearance and transmission to the .primordia of plastids and chondriosomes may be a daring hypothesis, but, if as there is good reason to believe, these bodies are permanent organs, there is no escape from some such assumption.
The reader is left with the feeling that the work has been carefully and thoroughly done, and that the conclusions are convincing.
W. D.
Some New Laboratory Methods.
Gussow, H. T. A new method for " hanging drop " cultures. Phytopathology 8 ; {1918) p. 447.
Instead of the usual drop suspended from the under side of a coverglass, the author recommends that the drop be flattened out into a thin film by means of a smaller coverglass placed over it. This keeps the culture in a thin layer, and permits examination of all parts with the highest powers of the microscope.
Bachman, Freda M. A bacteriological'method useful for the study of other microorganisms. Am. Jour. Bot. 5 1918 pp. 32-35.
Ordinary methods of the culture of bacteria are adapted so that the cultures may be grown on microscopic slides and made into permanent pre- parations. Bacteria when grown on a slide in a thin film of hard nutrient medium retain their normal position in the colony. The method has been
