1909] CURRENT LITERATURE 481 



nuclei resulting from the first division remain in the upper portion of the sac. One 

 of these divides to form the two synergids, and the other forms the egg and polar 

 nucleus. There are therefore no antipodals and only one polar nucleus. In 

 fertilization one male nucleus unites with the egg; the other unites with the polar 



form 



rms 



previous accounts of Gates. 2 * There is no fusion of parallel threads in synapsis. 

 The spirem later breaks into the vegetative number of chromosomes, which after- 

 ward become paired. The first mitosis separates whole chromosomes, and the 

 second separates the longitudinal halves of these. Certain critical stages during 

 the period between synizesis and diakinesis, which prove that the chromosomes 

 are formed by the segmentation of a single spirem thread, are not represented; 

 but these stages are the most difficult to obtain, probably because they are passed 

 through quickly. It seems now pretty evident that there are two general methods 

 of reduction in plants, as in animals, one involving a telosynapsis, the other a para- 

 synapsis or side-by-side pairing of chromosomes. 



The question of sterility is also examined, with interesting results. In Oeno- 

 thera Lamarckiana 50 per cent, of the ovules are found to degenerate, and about 

 50 per cent, of the pollen grains — two from each tetrad of spores. A large num- 

 ber of other Onagraceae were examined, nearly all of which were found to exhibit 

 more or less sterility. Geerts concludes that the sterility of O. 

 cannot be explained as the result of hybridization, cultivation, or lack of nutrition 

 or space, but that it has been inherited from a remote ancestor, probably from 

 the ancestor of the whole sub-family. He* thinks that since this sterility is herit- 

 able it must have originated by a mutation, or rather two mutations, one on the 

 pollen side and one on the megaspore side, since they are often sterile in different 

 degrees in the same species ! 



So far from explaining anything, it seems to the reviewer that this muddies 

 the pool and is much worse than a fiat confession of ignorance as to the cause. 

 It will be unfortunate if botanists acquire the habit of ascribing the origin of com- 

 plex conditions, such as sterility, to a sudden M mutation" in some ancestor. There 

 is no evidence to show that the sterility has not been gradually acquired, and for 

 that matter independently acquired, in the different species. To call it a mutation 



in neither its origin nor its cause. — R. R. Gates. 



Lamarckiana 



helps to explain neither its origin nor its cause.- 



Seedlings of conifers. — Hill and Fraine 25 have published a second paper 

 on the seedlings of gymnosperms, the thesis being that polycotyledony is attained 

 by the splitting of preexisting members, which were probably two in number. 

 In the present investigation seedlings of Tsuga, Abies, Picea, Cedrus, Pinus, 

 Larix, Pseudolarix, and Araucaria were studied. The general result shows that 



2 -* Gates, R. R., A study of reduction in Oenothera rubrinervis. Bot. Gazette 

 46:1-34. ph. 1-3. 1908. 



2 5 Hill, T. G., and de Fraine, E., On the seedling structure of gymnosperms. 

 Annals of Botany 23:189-227. pi. 15. Jigs. II. 1909. 



