182 SUMMARY OF CURRENT RESEARCHES RELATING TO 



BOTANY. 



GENERAL, 



Including the Anatomy and Physiology of Seed Plants. 



Cytology, 

 including: Cell Contents. 



Chromosomes of Asphodelus microcarpus.* — A. Maige has studied 

 the formation of the heterotype chromosomes in Asphodelus microcarpus, 

 and finds no support for Overton's theory as to the existence of pro- 

 chromosomes, nor for the theory of Gregory and Berghs of two spirems 

 existing side by side. Neither in the prosynapsis stage nor in the 

 synaptic stage is there any sign of such structures. The chromosome- 

 formation at first led the author to favour Farmer's theory, but subse- 

 quent closer examination has induced him to believe that Strasburger 

 and Gregory are correct in their descriptions and theory. One curious 

 condition observed in the present type is the delay of the longitudinal 

 splitting of the portions of the spirern. 



Structure and Development. 

 Vegetative. 



Gum-flow in Relation to Anatomy in Bromeliaceae.f — K. Boresch 

 has studied the flow of gum observed in connection with the Brome- 

 liacege in order to discover in what way it is related to the anatomy. In 

 over fifteen species the flow of gum is from the stem, the chief seat of 

 formation being the parenchyma of the stem, more especially the cortex. 

 In Pitcairnia Roezlii gum exudes from the lower part of the leaf. A 

 significant fact in connection with the origin of the gum-cavities is the 

 staining of their walls with ruthenium-red. In Quesnelia roseo-margi- 

 nata the gum can be stained with iodine-green. The walls of the gum- 

 cavities have remarkable thylose-formations, which often fill the cavities 

 themselves. Most gum-cavities are probably of lysigenous origin, but 

 some appear to be schizogenous. The gum in the first instance is 

 derived from the cell-membrane, but later on the cell-contents share 

 in its formation. Gum-flow may be produced artificially, and when 

 occurring naturally must be regarded as a pathological phenomenon, 

 the cause of which is unknown. It appears to originate in a circular 

 meristematic zone, which lies between the central cylinder and the cor- 

 tex, and extends from the growing point down into the lower parts of 

 the stem. The Bromeliacea; appear to be related in this respect to 

 those Monocotyledons having specialised cambial zones. Especially 



* Coruptes Rendus, cxlix. (1909) pp. 1084-8G. 



t SB. Akad. Wiss. Wien, cxviii. (1908) pp. 1033-80 (3 pis.). 



