212 SUMMARY OF CURRENT RESEARCHES RELATING TO 



BOTANY. 



GENERAL, 

 Including- the Anatomy and Physiolog-y of Seed Plants. 



Cytology, 

 Including- Cell-Contents. 



Mitochondrial Origin of the Plastids. — A. Guilliermoxd (Ann. 

 Sci. Nat. (Bot.), 1919, ser. x., 1, 225-47, 5 pis., 10 figs.). A paper 

 dealing with Mottier's recent work in connexion with the origin of the 

 mitochondrias (Ann. of Bot, 1918, 32). The latter writer claims to 

 have proved that plastids and mitochondrias are two different and 

 distinct constitutional elements of plant-cells. The present work is 

 intended to show that plastids are specialized forms of mitochondrias. 

 It is pointed out that in animal cells the mitochondrias have been 

 proved to perform the same functions as the plastids of plant-cells — 

 i.e. they elaborate different nutritive products and pigments. The writer 

 also claims to have proved conclusively that the yellow pigment of the 

 tulip is formed by the chondriocontes ; also, that the epidermal cells of 

 the leaf of Iris germanica contain amyloplasts which are identical in 

 every respect with the chondriocontes. It is admitted that mito- 

 chondrias and plastids may be formations of the same nature and 

 significance, but evolving separately and having distinct elaborative 

 functions — i.e. there are varieties of mitochondrias each specializied for 

 its own particular function. It appears preferable to regard both mito- 

 chondrias and plastids as different forms evolved from a common origin, 

 and the writer claims that investigations made by himself and other 

 botanists fully confirm the work done by animal cytologists, and show 

 that while some of the mitochondrias retain their primitive form, others 

 develop into chondrioplasts in the animal cell and plastids in the plant 

 cell. S. Cr. 



Structure and Development. 



Vegretative. 



Exudation of Water by Colocasia.— M. G. Flood (Sci. Proc. Eotj. 

 Soc. DiiMin, 1919, 15, 505-12, 2 pis., 1 fig.). The writer has studied 

 the leaves of Colocasia antiqiwrum in order to locate the gland or tissue 

 responsible for effecting the exudation or the filtration of the water. 

 .Rapid transfer of water through the petiole and blade is indicated by the 

 lacunae in the petiole, canals in the leaf, and spaces and perforations in 

 the mesophyll. These features, however, do "not support the hypo- 

 thesis that the water is secreted by cells in the tissues of the apex, or is 

 even filtered there." It was not possible to demonstrate by histological 

 methods the presence of continuous membranes under the pores in the 



