MEDULLARY BUNDLES IN LOBELIA PUBERULA

Abstract

Accessory vascular bundles may be fouind in the cortex of certain plants in the Melastomaceae, Calycanthaceae, Cactaceae, etc.; in the pithin members of the Piperaceae, Cucurbitaceae, etc., or even in the medullary rays, as in the transmedullary bundles of Citrullits vulgaris, Lagenaria vulgaris, and other cucurbits previously described by the writer (4). Accessory pith or medullary bundles may represent independent stem strands, as in certain Begoniaceae, Melastomaceae, etc., or leaf-traces which penetrate the stem as in Piperaceae, Cucurbitaceae, and Lobelia puberdal. The lastnamed species has beenl the subject of recent investigation by the writer. Westermaier (5) found a greater amount of translocated food in plants that live through the winter on reserves stored in tubers or rhizomes than in those which develop perennial woody shoots. Thus, in the former there is a greater demand upon the conducting system which may be met by the development of accessory vascular bundles, a feature seen in Lobelia pitberula. Plants having numerous flowers densely crowded together may develop accessory bundles to carry the requisite nourishment to all the developing seeds, as in certain species of Campanula. DeBary (I) found that the presence of large amounts of chlorophyll in the cortex may demand the development of an auxiliary conducting system, generally occurring in the form of cortical bundles, extrafascicular bundles previously described for M omordica (4), and ectoand endocyclic sieve-tube connections, as traced by Fischer (3). In Campanula raptunctloides medullary phloem and vascular bundles were described by Col (2) but the subsequent work of Ydrac (6) failed to find these in the Lobeliaceae. Lobelia puberula Michx. is a perennial herb growing in sandy soil from New Jersey to Iowa and south to Florida and Texas. In New Jersey it not infrequently attains a height of from four feet to five feet six inches, and not from one to three feet, as stated in some manuals. Differing from Lobelia cardinalis, L. inflata, L. siphilitica, L. erinus, and others which are perennial by offsets, L. puberitla is truly perennial, existing through the winter by food stored in its caudex. This fact is important when it is remembered that L. puberula alone of the above-mentioned species is provided with accessory bundles. METHODS