158 BOTANICAL GAZETTE [MARCH 
the beaks is probably to place the oosphere in a more favorable 
position and to attract and guide the pollen tube. 
In the relative size of the nuclei and nucleoli of the primary 
endosperm nucleus, oosphere nucleus, and nuclei of the syner- 
gids the same uniformity was observed which characterized 
these structures in Aster. Over two hundred measurements in 
Salix glaucophylla gave the following results. The average 
length of the primary endosperm nucleus is 11.2 m», and its 
breadth 10 »; the diameter of the nucleolus being 5.7. The 
oosphere nucleus is 8.8 » long and 7.8 » wide; and the diameter 
of its nucleolus 4“. The nuclei of the synergids are usually 
spherical, with an average diameter of 6.3; and the diameter of 
their nucleoli 2.34. All measurements were made from speci- 
mens which were ready for fertilization but had not yet been 
pollinated. The primary endosperm nucleus is always the lar- 
gest, the oosphere nucleus next in size, and the synergid nuclei 
the smallest. The nucleoli have the same relative size. Meas- 
urements in other species gave the same relative results. 
POLLEN TUBES AND FERTILIZATION. 
In 1891 Treub (22) made the discovery that in Casuarina 
the pollen tube enters by way of the chalaza instead of the 
micropyle. In 1893 Betula was found to be chalazogamic, the 
discovery being made independently and almost simultaneously 
by Miss Benson (26) in England and Nawaschin (25) in Russia. 
Miss Benson at the same time added Alnus, Corylus, and Car- 
pinus to the list, and Nawaschin soon added Juglans. 
In consequence of these discoveries the pollen tubes of 
Salix were traced with considerable interest. In S. glaucophylla, 
S. cordata, S. petiolaris, and S. wistis, many pollen tubes were 
found, entering invariably by way of the micropyle. The chal- 
azal region was examined critically in over three hundred ovules, 
but no trace of a pollen tube was found. The generative cell 
within the tube was observed but twice, and then under abnormal 
conditions (fig. 78). Ina few cases the male er was observed 
b ae Co ctulale Magara Bone = 
within the oosphere. The: . h to co tion which 
