I24 BOTANICAL GAZETTE [FEBRUARY 
abundant in one place only—a shallow region at the surface of the 
single heavy integument. Soon after the appearance of walls and 
long before the filling of the sac with tissue, the gametophyte becomes 
green. In a few weeks it is by far the greenest thing in the ovule. 
An alcholic solution of this green pigment gives the spectrum of 
chlorophyll. The presence of chlorophyll, evidently functional, 
within a gametophyte wholly enclosed within an ovule has not been 
reported before. The thin walls of the cells of the integument, the 
paucity of chlorophyll there, and the presence of numerous large 
cavities full of a clear viscid liquid favor the transmission of light to the 
gametophyte, and, as a meristematic tissue, it responds by the forma- 
tion of the pigment. WARMING (12) reports that the endosperm of 
Cycas circinalis, if fertilization fails to take place, sometimes grows 
out through the micropyle and in the light becomes green. No 
mention, however, is made of its becoming green before protruding. 
The cells of the endosperm early fill with starch, the large grains 
characteristic of the storage forms being abundant in the inner cells 
(jigs. 26-38), while smaller grains in all stages of formation are to be 
seen in the periphery. of 
Some of this starch is undoubtedly manufactured by photosyn- 
thesis within the prothallium, but some may be the result of absorp- 
tion from surrounding nucellar and integumentary tissues. Starch is 
plentiful, however, only in the outer layers of integument, never close 
to the endosperm. 
Spongy tissue 
The spongy tissue, in the midst of which the mother cell appears, 
performs an important function in the nutrition of the prothallium. 
As the megaspore mother cell forms the tetrad, the whole spongy mass 
increases in bulk, the individual cells multiplying by spindles at right 
angles to the periphery of the mass (fig. 39). The nucellar tissue 
immediately surrounding at once shows signs of being absorbed, the 
protoplasmic contents of the cells becoming dark and granular even 
before the walls suffer collapse (fig. 39). This mode of increase in 
bulk of the spongy tissue and the adaptation of the surrounding 
nucellar tissue is described at length by Miss FERGUSON (4) in her 
work on Pinus. The result of this activity is a growing mass, at first 
