THE ROOT SYSTEM OF LINARIA VULGARIS MILL.: I. MORPHOLOGY AND ANATOMY
The morphology and anatomy of the root system of Linaria vulgaris is described. The invasive behavior of the plant is related to the growth habit of the root system and to the formation of buds on the roots. The root system is described in terms of a framework of vigorous long roots, each passing through a phase of horizontal growth followed by a phase of vertical growth. Long roots bear lateral roots which mostly appear to be of restricted growth; long roots of the next order are generally initiated in the region where the direction of growth of the parent long root changed. Any lateral root is thought to be potentially capable of developing as a long root. There are no qualitative grounds for a separation of long and short roots, though most roots are restricted in their growth. Bud initiation is a feature only of roots which have developed as long roots. Root buds are not formed from the long root tissues, but from the bases of some of the lateral roots of the long roots, always in regions where the parent long root passed over from horizontal to vertical growth, and occasionally on the horizontal parts of long roots. Bud formation has only been found to occur when some secondary growth is present in the parent long root.