Page:The Journal of Indian Botany.djvu/772

268 THE JOURNAL OF INDIAN BOTANY. In plants, some of the mitochondria remain "inactive," that is, retain permanently their original form, while others develop into (1) amyloplasts, (2) chromoplasts, and (3) chloroplasts. This fact has led many investigators to conclude that the primordia of plastids are really not mitochondria at all, but are structures of an entirely different order. Such a view finds its strongest support in Cryptogams having one or few large chloroplasts, as in Conjugatae, Anthoceros, and Selaginella ; here the primordia of plastids are distinguished by their larger size, even in the youngest cells of the growing points. Guilliermond is convinced that such a distinction should not be made, because the staining and other reactions of plastid primordia are exactly those of "inactive" mitochondria, and even the size distinction disappears in Phanerogams and in fungi. He thinks that the most that can be said is that there are two kinds of mitochondria in the plant cell.

The function of "inactive" mitochondria is not known, though in animals where no other kind exists, they are believed by some authors to elaborate secretions and certain pigments, to play a part in oxidations, and to function in some way in heredity. Probably they have similar functions in plants.

Microsomes are more or less transient, minute, fat-like granules, variable in number, and distinguished in various ways from mitochondria. Nothing beyond the fact of their existence is mentioned; it is not even known whether they are of general occurrence in plant cells.

The vacuole system is a constant feature of plant cells, and arises in young cells from "vacuole primordia" lying close to the nucleus. These primordia so closely resemble mitochondria in appearance that some cytologists hold that they actually are mitochondria. They possess about the same fixing and staining reactions, but are distinguished in various ways. The author believes that absolutely no relation exists between the vacuole

system and the mitochondria that they are two quite independent systems superposed on each other in the cell. The primordia enlarge as the cell grows, they anastomose to form a network, and portions swell up to become the familiar vacuole system. The process of growth appears to be the result of hydration of the original substance of the primordia. The vacuoles probably are centres of elaboration of various substances, e.g., anthocyanins.

The paper is fully illustrated by figures from various authors, and a complete bibliography is given ; one is struck by the preponderance of papers in French. The author very skillfully emphasizes the deficiencies in our knowledge of cell morphology, and shows the need for an immense amount of the most detailed and painstaking investigation.

Hahn, Glenn G„ Hartley, Carl and Rhoades, Arthur S. Hypertrophied Lenticels on the Roots of Conifers and their Relation to Moisture and Aeration. Jour. Ag. Bes. 20 ; 253 — 265, 1920.

The authors observed warty excrescences on the roots of conifers, particularly Pinus ponderosa, as they were dug for shipment from a nursery in Nebraska. Microscopic examination reveals the fact that they are enlarged lenticels. Further search revealed such growths on the roots of twenty-one