ipoS] CURRENT LITERATURE 69 



TabernaemofitanixP. rubens, Syringa vulgaris XS. persicay and Mirabilis forms 

 including M, JalapaXM. tuM flora and J/. JalapaXM. longt flora. In some of 

 these the usual irregularities in the reduction mitoses of sterile hybrids are reported. 

 In Potentilla TahernaemontaniXP . ruhens the x number of chromosomes b 16. 

 The hybrid shows no difference from the parent P. Tabernaemontani in pollen 

 formation, except that the former produces a larger number of imperfect pollen 

 grains. In P. rtibens nearly all the pollen grains are good. The latter is a constant 

 species, while the former is very variable or "mutable." By subjecting this 

 hybrid to etiolation in hothouse temperature, complete sterility was produced. 

 The reduction divisions were apparently normal, but there was a lack of cytoplasm 

 and of chromatin, the scarcity of the former beginning as early as the archesporium 

 stage. Similar but less marked results were obtained by subjecting P. rubens 

 to the same conditions. Some of Tischxer's interesting conclusions, which will 

 be further discussed in the forthcoming paper, may be briefly stated as follows: 

 (i) Sterility of hybrids does not depend upon any form of chromatin repulsion. 

 (2) Sterihty results from the fact that two sexual cells are thrown together whose 

 developmental tendencies are not identical. When the individual reaches the 

 critical reproductive stage the disturbance of harmony in its development makes 

 itself apparent. (3) By modification of the external conditions in plants which are 

 not hybrids, the sexual cells may be so influenced as to produce conditions similar 

 to those which result from hybridization. (4) The steriHty of hybrids is a purely 

 relative matter. (5) A true splitting or segregation of characters does not occur 

 in the reduction divisions. One of the arguments in support of this conclusion is 

 that certain characters :Mendelize which concern not single rudiments but the 

 constitution of the whole of the idioplasm. (6) The assumption that the indindua 

 characters are connected with distinct and separated pangens is abandoned. (7) 

 The chromatin is not of exclusive significance as a hereditary sul^tance.^ (8) There 

 is a specific idioplasm having a definite constitution. (9) A distinction is to be 

 maintained between chromatin and hnin. (10) Apogamy is merely an aid in 

 reproduction in cases of poUen sterihty, and is not the primary condition to which 

 pollen obliteration is secondary, (ir) Similarly, as shown by Correxs, m species 

 which are passing from the monoecious to the dioecious condition, disturbance 

 similar to those of mutation occur, resulting in contabescence of the anthers or 

 ovaries. (12) There is, as D.ajrwix beheved, a dose relation bet^veen the stenh^- 

 of hybrids and that of plants under cultivation. The full account of this work 

 will be awaited with interest. — R- R. Gates. 



.^^^j of Aral!aceae.-A very comprehensive treatment of the Araiiaceae 

 has been published by ViGUizx," dealing with the history of the famuy, the extemai 

 morphological charactei^, and" the internal structure of stem and leaf ot about 

 sixty genera. Besides being a valuable contribution to the knowledge of plant 

 anatomv in general, the paper offers an exceUent proof of the nnponance ol aaa- 



'* VlGtllES, Ress, Recherches anatomiques sur 

 Ann. Sci. Nat. Bot. IX. 4:1-208. 1906. 



ia classification des Araliacees 



