m ] CURRENT LITERATURE 34 1 



that it has been clearly proved that the fungus of the host is necessary for the nor- 

 mal germination of the seeds of many orchids; but even here our knowledge is 

 of little scientific significance until we know the exact method of the action of the 

 fungus, whether its effect is due to the secretion of certain chemical compounds, 



water 

 Chromogens. — Tammes 



W'm. Crockkr. 



ent in all the genera and species of Dipsaceae examined. Dipsacan has many 

 points of resemblance to isatan and indican, yet it shows points of difference from 

 both these, as well as from the pseudoindicans of the Acanthaceae. At tempera- 

 tures above 35 C, in the presence of oxygen and water, dipsacan is transformed 

 to a blue pigment, dipsacotin. The optimum temperature for this transformation 

 is ioo° C. At high temperatures, or at ordinary temperatures through the action 

 of benzin, phenol, or dipsacase, an enzyme of this family of plants, dipsacan is 

 transformed to a yellow-red pigment in the entire absence of oxygen. Upon 

 admission of oxygen this pigment is transformed to dipsacotin. 



Palladin" has already urged that chromogens are universally present in 

 actively respiring portions of plants and that they are products of respiration. 

 Tammes's results agree with this conception, for dipsacan is found to be most 

 abundant in the most active portions of the plants and in those plants that arc m 

 the best condition for growth; otherwise only traces of dipsacan appe ar - 



Tammes 



pigment 



formation of the 

 on, as Pai.ladin 



ysis; but it is not known that sugar is also a product, 

 dipsacotin from the vellow-red pigment is a matter of 

 has shown is. the case in the production of the pigments from numerous enromo- 

 ns he has studied. It strikes one as possible that the formation of the chromat.c 

 materials in general requires both hydrolysis and oxidation. This would in- 

 U P all these chromogens with indican— Wm. Crocker. 



Germination and light.-KiNZEL" publishes another paper on the effect 

 of light on germination of seeds, confirming the results of former papers a 

 adding a number of species to those favored in germination by light. 



In a discussion of "after-ripening" he states that the several years flea, 

 ^nation shown by the ripe seeds of Thlaspi arvensc is due to the charac 

 *» embryo and not to the character of the coat, for the coat is very delicate 

 !^lejmblished in 1906/3 the reviewer has shown that the very marked y 



T^TWs, Tine, Dipsacan and Dipsacotin, ein neues Chromogen undein neuer 

 F arbstoff der Di psacea e. Recueil Trav. Bot. Neerland 5:- («M?-> ,g ° pflan7en 

 " Palladin, W., Die Verbreitung der Atmungschromogens bei oe 



f 



12 



B 



^tsch. Bot. Gesells. 26a: 378-389- 1908. . erganzende 



Bp Kixzel, WlLHEUr, Lichtkeimung. Einige bestat.gende und erga^ -. 



^erkungen zu den vorlaufigen Mitteilungen von 1907 " nd ««* "* ' 



^•Gesells. 263:631-645. 1908. . . r, OT Gazette 



"Crocker, Wm., Rule of seed coats in delayed germ.nauon. Bot. 



42: ^- 1906. 



