452 BOTANICAL GAZETTE [November 



to vary indirectly with the distance from the crown. Roots of French crab, 

 so extensively used in America as stock, are less hardy than roots from scions 

 of an average variety of apple. It is of considerable interest to note that 

 heavy dormant pruning, thinning of fruit, and application of nitrate fertilizers 

 prolonged the growth period, lengthened the rest period, and consequently 

 reduced the early forcing of growth in spring with subsequent injury by late 

 frosts. The selection of trees with long rest period also helps to obviate the 

 latter injury. Of apple blossom tissue, the pollen w r as found most resistant 

 to low temperature. 



The work presented in this bulletin is of such a character as to be of great 

 interest alike to those engaged in "pure" science and to those whose chief 

 interest is in the applied side. — L. I. Knight. 



Mitosis in Tetraspora. 



McAllister 6 



very 



sponds in its essential features with that in higher plants. In the cell which 

 is to give rise to 8 gametes, the resting nucleus contains a reticulum with net 

 knots and a nucleolus. During the prophases, the reticulum develops chro- 

 matic bodies which apparently become arranged in a row to form a spirem 

 thread. The nucleolus takes no part in this process. The spirem segments to 

 about 13 chromosomes, which divide and pass to opposite poles. Details of 

 spindle-formation w r ere not made out, but there was found no reason to believe 

 that Tetraspora differs from higher plants in this respect. Centrosomes or 

 centrospheres, which might be expected on account of their reported presence 

 in the gamete-forming cells of certain bryophytes, were not found. Cell- 

 division is brought about by the splitting of a granular cell plate formed by the 

 central spindle. The splitting takes place from the center outward. 



The second and third mitoses follow quickly, but in each case the daughter 

 nuclei enter the resting stage. The single pyrenoid of the original cell remains 

 unchanged through the three divisions, so that it comes to lie in only one of 

 the 8 gamete cells. In each of the other 7 cells one appears to arise de novo 

 from the cytoplasm. The entire pyrenoid is said to fragment to form several 

 starch bodies. 



Since Tetraspora and other green algae resemble higher plants so closely 



in mitosis and differ so widely from the Euglenidae, the theory that the Chlamy- 



domonadaceae, to which Tetraspora is held to be so closely related, have arisen 



from the Euglenidae is believed by McAllister to be excluded. — L. 

 Sharp. 



W 



Mitosis in Preissia. — In many papers dealing with mitosis in liverworts, 

 attention has been focused chiefly upon the centrosome and related structures. 



6 McAllister, F., Nuclear division in Tetraspora lubrica. Ann. Botany 27: 

 681-697. pL 56. 1913. 



