Los Angeles County Arboretum and Botanic Garden

The invasive azalea lace bug, Stephanitis pyrioides (Scott) (Tingidae: Hemiptera), is an important pest of Rhododendron (L.) (Ericales: Ericaceae). Feeding by nymphs and adults removes chlorophyll, reduces rates of photosynthesis and transpiration, and causes leaf stippling, which reduces the aesthetic value of infested plants. Rhododendron spp. are a major component of landscapes in the Pacific Northwest. Previous studies on the seasonality of S. pyrioides in North America are largely from the southeastern United States, which could have limited applicability in the Pacific Northwest. To quantify S. pyrioides seasonality in western Washington, we sampled ~200 leaves from 18 Rhododendron plants 1-2 times per wk from April to October over 2 yr, and microscopically counted the number of eggs, early instars, late instars, and adults. We developed a degree-day model for first generation S. pyrioides, which we used to estimate that S. pyrioides undergoes two full and a partial third generation in western Washington. Our model estimates 5 and 50% early instar occurrence, after hatching from overwintering eggs, at 69 and 171 accumulated degree-days from 1 January, respectively, when using a base threshold of 10.2°, which can be used to optimize the timing of management decisions. We also observed faster development and adult emergence when S. pyrioides nymphs feed on susceptible host plants relative to more resistant host plants, which may influence the timing of management decisions and potentially increase the probability of a full third generation. This research enhances our knowledge of an emerging invasive species in the Pacific Northwest.

The genus Haniffia is revised, in comprises two species of which one is described as new: H. albiflora from Thailand. Both species are illustrated.

The name Zingiber collinsii is validated and some corrections to an ealier publication are given.

Six new species of the genus Zingiber from Borneo are presented. Z viridiflavum was collected in primary lowland forest, while Z chlorobracteatum was collected in hilly secondary forest. Both are characterized by their slender fusiform inflorescences with yellow‐green bracts. Z. flagelliforme found in primary lowland forest displays a peculiar reproduction habit in its tapering leafy shoots which bend over to trail on the ground where plantlets produced in the leaf‐axis take root. Z velutinum was found in mid‐elevation secondary forest. It is a tall plant with large ovate inflorescences and bright red, densely hairy bracts. Z phillippsii was found in a gulley in montane primary forest. It is vegetatively characterized by its purple stems and glabrous leaves while the inflorescence has a similarity to the common Bornean species Z. coloratum. Z. georgeii is distinct by its procumbent inflorescences with orange bracts. Z viridiflavum, Z. chlorobracteatum, Z. flagelliforme, Z. phillippsii and Z velutinum are from Sabah and Z georgeii is from Sarawak.

Zingiber collinsii, a new species from Vietnam is described and illustrated. It is placed in section Zingiber having the inflorescence on a radical, short erect scape.

Recent collections from Sabah and Sarawak have revealed a wide species diversity among the Bornean members of the genus Zingiber. Four previously unknown and one incompletely known species of the genus are presented. Z. vinosum is a lowland species characterized by its burgundy colour of the lower surface of the leaves. Z. lambii was collected in primary lowland forest on ultramafic soil while Z. argenteum was collected in primary lowland forest on limestone. Both are characterized by their silvery leaves and orange inflorescences. Z. pendulum, found in primary mountain forest, has pending leafy stems and a deeply split labellum with very well developed side‐lobes. Z. latifolium, found in secondary mountain forest, is vegetatively distinct by its broad leaves with a densely pubescent margin Z. vinosum, Z. Iambii, Z. pendulum and Z. latifolium are from Sabah and Z. argenteum is from Sarawak.

Guayule (Parthenium argentatum Gray) contains rubber in the parenchymatous cells of stems and roots. Stem anatomy of P. argentatum is described along with that of P. incanum H.B.K. (mariola). Anatomy of these species differs significantly. Phloem rays in both species increase in width by cell division and expansion; however, the increase observed in mariola is less as compared to that in guayule. Axial xylem parenchyma in guayule is generally a two‐cell strand as compared to the fusiform axial xylem parenchyma observed in mariola. Vascular ray cells and cells of the pith region of guayule are parenchymatous, whereas those of mariola are sclerenchymatous. As a result of introgression between guayule and mariola, three forms of guayule exist in the native stands of Mexico. Morphological differences between these guayule plants have been described previously. The stem anatomy of these three groups of plants differ importantly. Group I guayule plants, least introgressed by mariola, have taller rays with the cells of pith region and vascular rays parenchymatous. Group III plants, highly introgressed by mariola, have a few to many cells of vascular rays and pith with lignified secondary walls and shorter rays. Many of the anatomical characteristics of group II plants, somewhat introgressed by mariola, are intermediate between group I and III plants.

The morphological and vascular characteristics of the nectaries of the species of the Monotropoideae (Ericaceae) reflect the morphology and declination of the flowers. These, in turn, are related to the pollination systems of the species. The nectaries of members of the Monotropoideae exhibit a range in form from slender, elongate projections, to short, stout ones, or to low ridges between the staminal bases.

Despite the potential contribution suggested from chromatographic studies of many groups, taxonomic conclusions based on paper chromatography alone may carry some inherent errors. In many instances chemical differences between taxa cannot be characterized by two-dimensional chromatography of crude extracts. Pigment diversity may go unnoticed in such a study, and conclusions based on simple chromatographic results may show too much similarity between the taxa being compared. The resolution of chromatographic separations of the often very complex mixtures encountered in crude plant extracts can be greatly improved by a preliminary column separation, and in this study a method of pigment analysis employing both preliminary column and subsequent paper chromatography is used. While it is usually impractical to identify all of the components of a flavonoid complex, each member should be characterized to the degree that it can be distinguished from all others. Here, the characterization of a component includes its rate of movement in the column, relative position and color under ultraviolet light on the chromatogram, the absorption spectrum in ethanol and the change in the absorption spectrum when a reagent is added to the ethanol which has a particular effect on the spectral properties of that flavonoid. With very few exceptions no one criterion of characterization is definitive for any component. More than 20 flavonoid pigments have been observed in the two tetraploid Gossypium species, G. barbadense and G. hirsutum. Only 10 of the constituents were common to the two species. The results of a previous study based on two-way paper chromatography of crude extracts makes the two species appear much more similar in flavonoid composition than is indicated by the more detailed column-paper chromatography presented here. The degree of difference between G. hirsutum and G. barbadense is surprisingly large in light of the generally accepted theory of their common origin. The value of chromatographic-chemotaxonomic studies is greatly increased if the chemical systems involved are characterized.