552 SUMMARY OV CURRENT "RESEARCHES RELATING TO 



cell and spores have a well-developed chromosome at every stage of their 

 development, but the male cells have no chromosomes. The chromo- 

 somes of A. Husnoti and A. punctatus contain pyrenoids of a distinctive 

 character, consisting of a varying number of separate granules ; these 

 chromatophores may be regarded as transition-forms between those 

 having no pyrenoids and those containing simple pyrenoids, which are 

 characteristic of some species of Anthoceros. 



Mitochondrias and their Transformation into Plastids.* — A. 

 Guilliermond discusses the results of recent investigations concerning 

 the nature and function of mitochondrias. The opinion that these 

 bodies have no real existence, but are the result of experimental methods, 

 is shown to be incorrect, for both simple mitochondrias and chondrio- 

 konts can be distinctly seen in the living epidermal cells of Iris germanica. 

 The flower of the same plant also shows all stages of transition between 

 chondriokonts and amyloplasts ; it can also be proved that chromoplasts 

 of carotin and xanthophyll owe their origin to mitochondrias. The 

 iodin-test indicates the presence of starch in the interior of living mito- 

 chondrias, thus proving that starch is a direct product of their activity. 



Mitochondrias have well-defined morphological and histochemical 

 characters and definite physiological functions. Their simplest morpho- 

 logical structure is that of granules isolated or in chains ; the more 

 characteristic form is that of little rods. The chemical characters appear 

 to indicate the presence of an albuminoid substratum saturated with 

 lipoids. Their origin is uncertain, but there is ample evidence that they 

 multiply by fission. The only physiological function of which there is 

 definite proof is that of secretion of a very varied character. They 

 appear to correspond to the mitochondrias of animal cells, where they 

 are organs of the same rank as the nucleus, being present in all secretion- 

 phenomena and perhaps playing a part of the highest importance in the 

 differentiation of the cell. They are of equally wide distribution in the 

 plant-world, and there is every indication that their secretive function is 

 as varied as in animal cells. 



Mitochondrias of Higher Plants. f- -A. M. Lowschin has studied 

 the mitochondrias of higher plants, and now publishes a preliminary 

 paper dealing with results of experiments performed in order to discover 

 the connexion between the number of mitochondrias and conditions of 

 illumination, assimilation of C0 2 , etc. The author finds that there can 

 be no doubt as to the existence of mitochondrias in the leaves of higher 

 plants. In the palisade-parenchyma they are almost always granular, 

 but under abnormal conditions, e.g. in the dark, chondriokonts may be 

 found. In the spongy parenchyma there are granular or rod-like mito- 

 chondrias or chondriokonts. In the conducting tissues the latter form 

 is the most common. In the epidermis all three forms occur, but chon- 

 driokonts predominate and often reach a considerable size. In some 

 species, e.g. Quercus pedunculatus, they are absent under normal condi- 

 tions, but appear in the dark. In a few plants, e.g. Selaginslla Martensii, 



* Ber. Deutsch. Bot. Gesell., xxxii. (1914) pp. 282-301 (2 figs.), 

 t Ber. Deutsch. Bot. Gesell., xxxii. (1914) pp. 266-70 (2 pis.). 



