ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 605 



gametophyte stage in Apocynum androscemifolium. The chief points of 

 interest are the origin of the tapetum from the homologue of the 

 primary sporogenous layer instead of the primary tapetal layer, the 

 gradation between bilateral and tetrahedral development of the pollen 

 grains, the absence of a primary parietal cell in the ovule, and the single 

 layer of cells composing the nucellus. There is also a general similarity 

 to the internal structure of the flower in Asclepias. 



Development of the Embryo-sac and Embryo of Batrachium 

 longirostris.* — L. C. Riddle finds that the number of stamens in the 

 flower of this species varies from 17 to 21, the number of carpels being 

 approximately half as large ; the mature ovule is enveloped by a single 

 integument, traces of a second being seen in earlier stages. The 

 microspore-mother-cell forms four microspores ; no cases of more were 

 found, as has been reported in Ranunculus Fkaria and other Ranuncu- 

 laceas. Scarcely one in four of the microspores germinates. Just 

 before pollination the generative cell becomes lenticular, and divides to 

 form the sperm nuclei. In the megasporangium the occurrence of two 

 or more archesporial cells is frequent ; the remains of other archesporial 

 cells can almost always be seen around the megasporocyte. There is no 

 evidence of the cutting off of any primary parietal cell, but the reduc- 

 tion division occurs at once. The lower of the two cells divides first, 

 and in many cases the division of the upper seemed never to pass 

 beyond the formation of the spindle. The functional megaspore passes 

 through the usual divisions ; the definitive nucleus- was distinguished by 

 its enormous size. Fertilisation was not observed. In the embryo the 

 suspensor is short, and does not seem to function long after the forma- 

 tion of the endosperm. The cotyledons are small compared with the 

 hypocotyl, and the embryo is straight. The entire embryo-sac is filled 

 with endosperm cells of varying shapes and sizes, which contain abun- 

 dance of starch. The inner wall of the carpel is made up of a layer of 

 elongated cells, which are longest in the plane at right angles to the 

 axis of the carpel. Next to these are a few layers elongated at right 

 angles to the first and rather crescentic. As the ovule matures, these 

 cells develop thick perforated walls, while the cells beneath the epidermal 

 layer become somewhat separated to form a delicate spongy tissue. 



The same author | has described the development of the embryo-sac 

 and embryo of Staphylea trifoliata. The single archesporial cell develops 

 a row of 3-5 tapetal cells, by which the spore-mother-cell is pushed deep 

 into the tissue of the nucellus. The spore-mother-cell divides to form 

 four megaspores, the lowest only of which is functional. The embryo- 

 sac is typical, and the course of development of embryo and endosperm 

 is quite normal. 



Seed-Development in the Piperales.J — D- S. Johnson has studied 

 the development of the genera Anemiopsis and Houttuynia of the family 

 Saururaceae, and also representative genera of the Chloranthaceae and 



* 



Ohio Naturalist, v. (1905) pp. 353-63 (3 pis.), 

 t Tom. cit., pp. 320-5 (2 pis.). 

 \ Johns Hopkins Univ. Circular, New Series, 1905, No. 5. 



Oct. 18th, 1905 2 



