640 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Chlorophyll - grains and Chromatophores.* — Dr. A. F. W. 

 Schimper publishes a very exhaustive treatise on this subject con- 

 taining details of fresh observations and a resume of the work of other 

 observers. 



The nucleus is wanting in no living vegetable cells, with the 

 doubtful exception of the Schizoraycetes ; in addition to the nucleus 

 are other protoplasmic structures, known as chromatophores, from 

 their capacity of producing pigments. They are formed exclusively 

 from chromatophores previously in existence, never by new formation 

 from the cell-protoplasm. The author has detected these structures 

 in the ovum-cell and embryo-sac of Hyacinthus non-scriptus, Daphne 

 Blagyana, and Torenia asiatica, and in the ovum-cell of Atrichum 

 undulatum and Anthoceros Isevis among Muscinea3. They are always 

 present in growing points. In the lower Algae there is uniformly in 

 the earlier cells a single large chromatophore in each cell, while the 

 more highly differentiated later cells contain a large number of small 

 chromatophores. The same is the case upwards to the simplest 

 Muscinefe, e. g. Anthoceros. The simplest Florideae — the Bangiaceae 

 and the true Nemalieae — have a single chromatophore in each cell. 

 In almost all plants the chromatophores change their form as the 

 plant developes. 



In the lower plants, the simpler Chlorophyceae and the Diatomeae, 

 the formation of leucoplasts is a subsequent process, a transformation 

 of the coloured into a colourless chromatophore, while in the higher 

 plants it is usually the reverse transformation that takes place. The 

 Characeae are the lowest plants in which the leucoplasts have an 

 important physiological function ; in the Muscineae they play but 

 little part ; in the Pteridophyta and Phanerogamia they are much 

 more important. The same is the case with the chromoplasts, 

 which occur but rarely in the Chlorophyceae. The chromoplasts 

 are always formed at the expense of chloroplasts or leucoplasts. For 

 the chromoplasts of the Phaeophyceae the author proposes the term 

 phaeoplasts ; for those of the Florideaa rhodoplasts. 



With the exception of the Anthoceroteae, where there is usually 

 a single large chromatophore in each cell, those of the Muscineae are 

 very small and numerous, disc-shaped or polygonal. The chromato- 

 phores of the Pteridophyta do not differ essentially from those of 

 flowering phants. Leucoplasts are found in all those parts of Phanero- 

 gams which are completely excluded from light ; in many of the parts 

 exposed to light which perform other functions than those of assimi- 

 lation ; and in some saprophytes and parasites. 



The simplest chromatophores consist of a colourless protoplasmic 

 substance without any visible internal structure or contents ; and this 

 is sometimes the case during the whole of their existence, as with 

 most leucoplasts. But usually the protoplasmic structure or stroma 

 produces — mostly in its interior, less often on its surface — structures 

 of various kinds. The chemical nature of the stroma is very little 

 known ; the protoplasm of the chromatophores has been termed by 

 Strasburger chromatoplasm. 



* Pringsheim's Jahrb. f. Wiss. Bot., xvi. (1885) pp. 1-247 (5 pis.). 



