250 



BOTANICAL GAZETTE 



r- 



itf 



^R 



agents proved entirely satisfactory. Flemming's triple ntrtun 

 gave good results for pollen tubes and early stages in the develop- 

 ment of the archegonia, but by far the most satisfactory stain 

 was Haidenhain's iron alum-haematoxylin. Delafield's haema- 

 toxylin combined with orange G was best for embryos. Secti0ns 

 were cut 3 to 5 ^ thick. 



>p 



THE POLLEN GRAIN AND POLLEN TUBE. 



F 



No attention was given to the formation of microspores 

 from the mother cell, their study being taken up shortly after 



Uig^ 



The appearance of the 



/. 



It 



MeVhods 



pollen grains at the time of shedding is shown in 



does not appear that prothallial cells are cut off. 



which easily demonstrate the prothallial cells of Pinus a'nd sum- 



lar forms have failed to show any such structures in "Thuja, 



However, considering the ephemeral nature of prothallial cel!'^ 



o^ 



in most gymnosperms, and the small size of the microspor > 

 Thuja (20/X in diameter), it is possible, though not probabiO, 

 that they may have been overlooked. So far as could be deter- 

 mined, the next step after the separation of the tetrads is the 

 organization of a tube nucleus and a generative cell {fig* ^)' 

 The microspores of Cupressus Beiithamiana and of Biota orientaits 

 seem in every respect like those of Thuja occidentalism 



In material collected June 2, 1901, the pollen tube had pene- 

 trated a short distance into the nucellus {figs. J -4)^ '^^^ ^ "' 

 erative cell had already divided, and both the tube and siaU- 

 nuclei were in advance, and close against the large bod}" c 

 One of these nuclei is invariably somewhat smaller th:. 1 tii 



1. 



other. 



fig 



smaller nucleus is not shown, as it iiv 



immediately beneath the larger one. Conspicuous protopia&m 

 streams radiate from the tube and stalk nuclei downward tc ^ 

 end of the pollen tube, but little cytoplasm is foun^ auov 

 body cell. The nucleus of the body cell is in gener:.- ^ ' 



w 



the 



rjrsi 



1 



and is [surrounded by a thick sheath 



c^-- 



A deeply staining spot, presumably kinoplasmic in .i«*vare. 

 in the cj^toplasm. Strasburger (11) shows this ^^X)t ^n 



