The Pollen-stigma Interaction: Pollen-tube Penetration in Crocus

In a compatible pollination in Crocus, pollen tube tips enterthe stigma papillae after the enzymic erosion of the cuticle,and the tubes continue downward growth towards the ovary betweenthe cuticle and the underlying pectocellulosic wall. The cuticleof the receptive zone of the stigma papilla is chambered, thechambers containing a secretion accumulated during the maturationof the stigma. Pollen exudates contain various acid hydrolases,but are incapable alone of eroding stigma cutin. Furthermore,there is no penetration when the proteins of the wall-held stigmasecretions are degraded enzymically. These facts are taken toindicate that the pollen contributes a ‘cutinase’precursor which is activated by a factor or factors held inthe stigma secretion. Pollens of certain Cruciferae producetubes capable of penetrating the Crocus stigma cuticle, suggestingthat notwithstanding the taxonomic remoteness of Cruciferaeand Iridaceae the enzyme activation systems are quite similar.     

MODALITES DE LA DIFFERENCIATION DES CARACTERES SEXUELS SOMATIQUES DE NEREIDIENS (ANNELIDES POLYCHETES)

The influence of the age, of the fast and of the temperature with the differentiation of sexual somatic characters has been studied in some Nereids. The sexual somatic characters can be differentiated in Nereis of any age if the cerebral endocrine inhibition of the heteronereidation is suppressed. The supranormal temperatures release prematurely and accelerate the process of the differentiation of these characters; the low temperatures moderate these phenomena without preventing their apparition. The fast do not influence the differentiation of the somatic sexual characters.     

Seasonal heterophylly and leaf gland features in Triphyophyllum (Dioncophyllaceae), a new carnivorous plant genus

Triphyophyllum peltatum (Dioncophyllaceae), a tropical-West African liane, is heterophyllous, bearing leaves of three types, two on juvenile, non-climbing, short shoots, and the third on the mature axis. The short shoots produce mostly eglandular, lanceolate leaves, but just before the height of the rainy season small clusters of relatively ephemeral, glandular, filiform leaves are formed. These glandular leaves bear both stalked and sessile glands, and they act as efficient trapping organs for the prey, mostly flying insects and other small animals. The stalked glands, of which there are two size classes, are the most anatomically elaborate known in the plant kingdom. Structurally there are similarities with the stalked glands of Drosophyllum and Drosera. At maturity they carry secretion droplets, and stimulation by the prey leads to further secretion. The secretions contain a range of hydrolytic enzymes.
During sonic periods of its development Triphyophyllum is probably carnivorous. An important source of nutrients is thus tapped which could be significant in making possible an earlier transition from the juvenile to the rapidly-climbing adult form.
The Dioncophyllaceae, contains two other monotypic genera, neither with the carnivorous habit. Triphyophyllum is considered as an ecological African analogue of Nepenthes.     

The larval crustacean dorsal organ and its relationship to the trilobite median tubercle

In the dorsal median anterior region of the head, the larvae of decapod Crustacea possess a discrete organ: a glandular-sensory complex which is not present in post-larval juvenile forms. Its external topography reveals the presence of one or two central pores (Brachyura, Anomura) or a poreless central area (Macrura) surrounded by four equidistant plate-pits which contain a central pimple or 'nipple'. The Macrura plate-pits lack the central pimple but develop a row of diminutive pegs. No definite function can yet be ascribed to the organ. The dorsal organ described here in Decapoda larvae closely resembles the median sensory tubercle found on the cephalon of some trilobites, especially Trinucleidae. In view of the possible homology between these structures in the two groups, previous interpretation of the trilobite organ as a median eye tubercle must be rejected.