244 BOTANICAL GAZETTE [SEPTEMBER 
when compared with aerobic growth. He also finds no coincidence between 
intensity of “intramolecular” respiration and of anaerobic growth. e con- 
clusions of these workers are drawn from too few and these mainly cultivated 
forms. Study of wild forms of varied habits may show very different results. 
—WILLIAM CROCKER. 
Structure of the spore wall.—A notable addition to our aide of the 
structure and development of the spore wall is contributed by BEER in a 
study of the young pollen grains of [pomea purpurea. At the conclusion of 
the reduction division, the tetrads of young pollen grains become surrounded 
by massive mucilaginous walls, which show the reactions of callose and pectose. 
Within this mucilaginous wall, and surrounding each young pollen grain, 
i with th 
awkward and misleading term “special mother cell wall. e exine is 
deposited by the pollen protoplast upon the inner surface of the special wall, 
and at first is homogenous, but soon becomes differentiated into an outer 
lamella, with a network of thickening bands on its inner surface, and at the 
‘intersection of the bands are the rudiments of the spines. At this stage a 
clear space is seen between the outer lamella and the thickening bands, and in 
this space the rodlets characteristic of the mature pollen develop. The spines 
project into the pollen cavity before they begin to appear externally. The 
intine develops within the exine as a thin layer, with thicker portions where 
it protrudes into the exit pores. Chemically, it consists of pectic bodies 
associated with some cellulose. In older pollen grains the exine consists of a 
delicate outer lamella perforated with countless pores, so that it really forms a 
reticulum with open meshes, beneath which are the thickening bands con- 
stituting the mesospore, perforated by the narrow exit pores for the pollen 
tubes. The outer lamella of the exine dips into the exit pores and covers the 
protrusions of the intine at these spots. Since nearly the entire growth of the 
rodlets and spines takes place after they have become separated from the 
protoplast, it is concluded that they are able to develop without any direct 
contact with the protoplasm. 
This short paper presents a thorough study of a single species and suggests 
a series of investigations, for it may be predicted with the utmost confidence 
that the account will not hold for angiosperms in general, and the author 
makes no such claim. After various types of pollen grains have received 
similar attention, it will be time to generalize—CuartEs J. CHAMBERLAIN. 
Chemotaxy.—SuiBaTa* gives the first part of a full statement of his exten- 
sive work on chemotactic responses of the spermatozoids of pteridophytes. This 
3 _ Rupotr, Studies in spore development. Ann. Botany 25:199-214. 
pl. 13. 19 
3? SurpaTa, K., Untersuchungen iiber die Chemotaxis der Pteridophyten Sper- 
aaa “Jah b Wiss. Bot. 49:1-60. 1911. 
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