How the biophysical properties of overlaying tissues control growth, such as the embryonic root (radicle) during seed germination, is a fundamental question. In eudicot seeds the endosperm surrounding the radicle confers coat dormancy and controls germination responses through modulation of its cell wall mechanical properties. Far less is known for grass caryopses that differ in tissue morphology. Here we report that the coleorhiza, a sheath-like organ that surrounds the radicle in grass embryos, performs the same role in the grass weed Avena fatua (common wild oat). We combined innovative biomechanical techniques, tissue ablation, microscopy, tissuespecific gene and enzyme activity expression with the analysis of hormones and oligosaccharides. The combined experimental work demonstrates that in grass caryopses the coleorhiza indeed controls germination for which we provide direct biomechanical evidence. We show that the coleorhiza becomes reinforced during dormancy maintenance and weakened during germination. Xyloglucan endotransglycosylases/hydrolases may have a role in coleorhiza reinforcement through cell wall remodelling to confer coat dormancy. The control of germination by coleorhiza-enforced dormancy in grasses is an example of the convergent evolution of mechanical restraint by overlaying tissues.

See " Effect on young cane-' dead hearts,' " p. 5.) As many as 100 THE SUGAR-CANE MOTH BORER. 6 plants per acre may be destroyed, but so many plants remain in the field that this loss is not great. It should be prevented, however, because it is on these young plants that the borers multiply in sufficient numbers to become a serious menace to larger canes. Under calculable losses the injury to mature cane alone will be considered. The full amount of injury is shown only by chemical analysis. Infested and uninfested cane from Texas, not affected by red rot, a disease which often follows borer damage, was analyzed, with the following results Uninfested.

In this paper we describe the very peculiar life-history2 of Chelonus texanus Cresson. In brief the adult Chelonus deposits its eggs in the eg!!;sof its hosts but the parasite emerges not from the egg, but from the larva developed therefrom. Oviposition in the host's egg' and retarded development of the parasite to permit the host to hatch and grow to considerable size has been pointed out by Marchal (Summarized by Bugnion, 1907. Smithsonian Report for 1906. pp. 310-314) with reference to the Encyrius fuscicollis Dalman which oviposits in the eggs of Hyponomeuia malinella, etc., and by Silvestri (Biologia del Liiomastix irt/llcaicUus (Dalm.). Portici, pp. 4, 5, 10. 1906) with reference to Litomastix iruncateUus Dalman. which oviposits in the eggs of Plusia gamma Limucus and other Lepidoptera .. Litomastix truncatellus is polyemhryonic and possibly prndogenetic in alternate generations; Encyrtus fuscicollis is also polyembryonic, hut the Chelonus we have observed is a single and simple parasite. The Litomastix adult measures only 1.9 mm: in length and the egg of Plusia measures 0.6 mm. in diameter. Chelonus measures fully 5 mm. and the eggs of Heliothis measure about 0.5 mm. in diameter, while those of Laphygma are still smaller. Thus the contrast is much more striking when one observes Chelonus ovipositing than it would be in observing Litomastix.

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