The roots of plants are the least known, least understood and least appreciated part of the plant."-^\Veaver and Bruner (125).The underground parts of perennial grasses serve not only as anchorage and organs of absorption of water and nutrients, but also for the storage of reserves, and there exist significant interrelations between herbage growth and underground development. The aim of modem grassland husbandry is to produce and maintain maximum yields of high qiiality fodder. To achieve this, an imderstanding of the functions of the undergromid organs, their relations to the aerial parts, and their responses to environmental factors and cultviral treatments appears indispensable. Our knowledge on this subject is still fragmentary, and it is hoped that this reView of available evidence will stimulate further research on these matters.
SEASONAL UNDERGROUND DEVELOPMENTOnly a limited amount of work has been undertaken regarding the seasonal development of the roots and other underground organs of grasses. According to Trowbridge and co-workers (1) the weight of the corms of Phleum pratense, growing under Missouri conditions, was lowest in spring, and increased rapidly to the early bloom stage and then more slowly to maturity. Brown (2), also working in Missouri, found that spring and autumn were the more favourable seasons for root and rhizome growth in Poa pratensis. Root growth was most active during early spring at mean temperatures below 60°F, whereas rhizomes developed most rapidly in late spring and early summer. Both roots and rhizomes usually lost weight during summer at mean temperatures near or above 80°F.In Germany, Remy (3) obtained evidence that in Dactylis glomerata, grown in the greenhouse, the weight of the root system increased from mid-summer to late autumn. The seasonal root development of the same species was studied at Aberystwyth by Stapledon and Milton (4), who found that in plants grown in the open, root development was progressive from April to September. Sturkie (5) found that the root-stocks of Sorghum halepense developed after the aerial parts had matured, and according to Sampson and McCarty (6), root growth in Stipa pulchra occurred in autumn and winter when herbage growth had practically ceased, SimUar observations were made by Weinmann (7) on Chloris gayanq,, Rhodes grass. 115