The American genera of Malvaceae—II

The genera of Malvaceae that occur in North, Central, and South America (including the Caribbean) are enumerated, described, and distinguished, using an artificial key. The usual taxonomic information (bibliographic citations, synonyms, type species, etc.) is presented and the generic names are indexed. The literature is reviewed and summarized for each genus, presenting such information (where appropriate) as the etymology of the name, number of species, infrageneric classification, distribution, chromosome numbers, economic importance, distinguishing features, and reference to representative illustrations. Where useful, the taxonomic history of the genus is summarized. A listing of unresolved taxonomic problems in the family is presented to highlight needs for future study. A detailed bibliography is included. One new combination is made:Palaua sandemanii (Sandwith) Fryxell, based on the PeruvianMalvastrum sandemanii Sandwith.

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Resumen  Los géneros de la familia Malvaceae que se encuentran en Norte América, Centroamérica, y Sudamérica (incluyendo Las Antillas) se enumeran, describen, y distinguen por medio de una clave artificial. Se presentan informaciones tales como citas bibliográficas, sinonimías, y especies tipos para cada género, y se presenta un índice de los nombres, genéricos. Para cada género del que existe información, se presentan datos derivados de la literatura sobre su etimología, número de especies, clasificación infragenérica, distribución geográfica, números cromosómicos, importancia económica, características destacables, y referencias de ilustraciones representativas. Cuando se considera necesario, se presenta la historia taxonómica del género. Se presenta un lista de aquellos problemas taxonómicos no resueltos en la familia y se indican los estudios necesarios para el futuro. Se acompanya una bibliografía detallada. Se hace una combinación nueva:Palaua sandemanii (Sandwith) Fryxell, basada enMalvastrum sandemanii Sandwith.

     

Contributions to the mathematical theory of epidemics—II. The problem of endemicity

(1) A mathematical investigation has been made of the prevalence of a disease in a population from which certain individuals are being removed as the result of the disease, whilst fresh individuals are being introduced as the result of birth or immigration. Allowance is made for the effects of the immunity produced as the result of an attack of the disease, but the effect of deaths from other causes is not taken into account, and the action of the disease is supposed to be independent of the age of the individual. (2) As a special case of the above, results have been obtained for a closed population in which no deaths occur and to which no fresh individuals are added, but in which the individuals after being infected acquire immunity, and then may be again infected. A threshold density of population exists analogous to that described in the previous paper, which is such that no disease can exist in a population, the density of which is below the threshold. (3) In other special cases investigated when either immigration or birth is operative in the supply of fresh individuals, as well as in the general case, only one steady state of disease is possible. To reach this state the population must be of a certain density which will be determined by the functions characterizing the infectivity, morbidity, etc., of the disease. (4) Increase of the immigration rate or of the birth-rate results in an increase in the rate of infection of the healthy individuals and also in the percentage rate of infection, the percentage of sick, and in the percentage of mortality from the disease. This result is, of course, a necessary consequence of our assumption that the disease is the only cause of death. (5) More particular results have been obtained by substituting constants in the place of the undetermined functions assumed in the general theory. Further, under these conditions the nature of the steady states has been more fully investigated and it has been shown that in all cases, except one, the steady states are stable ones. In the exception, a disturbance would result in purely periodic oscillations about the steady state.     

LOBAR PNEUMONIA—The Distribution of Sites in Infants and Children

In a review of roentgenograms of 228 pediatric patients with segmental pneumonia, the left upper lobe was observed to be involved in only 4 per cent of cases. The right upper lobe was involved most frequently—over eight times as often as the left upper lobe and twice as often as the right middle or lower lobe. It is suggested that this distribution is related to the fact that the angle of the left bronchus in relation to the median plane is more acute than the angle of the right bronchus, the sharper angle perhaps serving as protection against aspiration.     

Energy and biological evolution—II. The mathematical structure of equilibrium states

We examine certain mathematical structures presented in Part I. The most important of these are the energy structures determined by the couple (ω×E, ψ) the space of causality defined by ψ^-1(0) and the notion of collapsibility, i.e., the descent of a species from a higher to a lower equilibrium configuration as a result of energy loss. This work was supported by an Associateship of The International Centre for Theoretical Physics, P.O. Box 586, Miramare, 34100 Trieste, Italy.     

The origin of mentha — gracilis (Lamiaceae). II. essential oils

Essential oils were eamined in nine clones of Mentha arvensis, four clones of M. spicata, and 20 clones of M. gracilis. An F₁ hybrid of M. arvensis M. spicata, selected on the basis of morphology and chromosome number, was matched with one clone of M. Gracilis. Genes for the inheritance of limonene, 1,8-cineole, linalool, isomenthone, carvone, and piperitenone oide were identified in one clone of M. arvensis and two clones of M. spicata. The range of essential oil compounds detected indicates that no one character can be used to identify M. gracilis, but the critical compounds of the oil of M. gracilis can be derived from crosses of M. arvensis M. spicata.