246 . BOTANICAL GAZETTE 



[masch 



sperms 



sperms 



that an integument of free segments is 

 gments, and that probably intermediate 



cence occur in the Lagenostoma group. In this group, therefore, the origin of 



integument 



Oliver is not inclined to accept Miss Benson's suggestion that the integument 

 (as illustrated by that of Lagenostoma Lomaxii) has arisen by the sterilization of 

 the peripheral sporangia of a synangium; but prefers to regard it as a new struc- 

 ture, arising contemporaneously with the seed habit, and related in some way 

 to the "encasement" that so often accompanies reproductive activity. 



The reasons for regarding Physostoma as a member of the Lagenostoma 

 group are given in detail, and the conclusion is reached that it is the "most primi- 

 tive seed yet come to light," the plant to which it belongs probably being one of 

 the Lyginodendreae. The reasons for the conclusion quoted above are not quite 

 clear, and seem to contradict some rather convincing conclusions reached by the 

 same author in his study of Stephanospermum and other paleozoic seeds— J. M. C 



Sterility in hybrids.— Tischler 6 has a lengthy treatment of the subject of 

 sterility in hybrids. A preliminary paper, summarizing his conclusions, has 

 already been reviewed in- this journal.' The present paper is in two parts, the 

 first presenting the cytological data and the second dealing with the theoretical 

 conclusions. The use of charcoal in drawings can scarcely be recommended for 

 clearness, many of the figures being mere smudges, and they furnish no sufficient 

 evidence of such cytological matters as the pairing of threads in synapsis. Pollen 

 formation, and in some cases megaspore formation, is described in hybrids of 

 Mirabilis, Potentilla, and Syringa. A variety of irregularities, such as are com- 

 mon during the reduction divisions in hybrids, are described, including formation 

 of extra nuclei by chromosomes left in the cytoplasm and failure of one or both 

 reduction mitoses. In other cases the reduction processes were normal, but there 

 was a lack of cytoplasm and the pollen grains failed to grow. PotenMa rubens, 

 cultivated in dry and hot conditions, matured good pollen, but after fertilization 

 the young embryos died. In all cases a paucity of cytoplasm was observed, begin- 

 ning during or after reduction. 



Tischler 



lack of harmony 



,7 wrea me cmomatic elements. However, it seems necessary to assume ^ 

 ^compatibility" of the chromatins or plasms, which makes itself evident 

 during the formation of reproductive cells, for otherwise there is no explanation 

 . why a plant continues to show vegetative growth and yet fails to mature its ge«° 

 cells. Instead of a chromosome incompatibility, perhaps we may have in u» 



TlSCHLE 



X: 33-151- fig*. 120. 1908. 



Arch 



Gaze 



