jSTijchols, A morphological study of Junipenis communis var. depressa. 233 
The microspore mother cells enter synapsis ahout May 1 st . 
Preparatory to this period a pairing of different portions of the 
chromatin becomes evident. 
At the completion of the heterotypic division two resting 
daughter nuclei are formed, hut a wall is never developed be- 
tween them. The second division may he either tetrahedral or 
bilateral. 
Preparatory to the formation of microspores the cavity of 
the mother cell becomes divided into fonr chambers by thick, 
transparent walls. Within these compartments the spores are 
developed, and they are eventually set free bythe breaking down 
of the enveloping walls. 
Pollination occurs about May 25 th . 
The elapsedtime between pollination and fertilization is about 
twelve and a half months. 
Düring the first season's growth the pollen tube penetrates 
a short distance into the nucellus and frequently branches, while 
the primary nucleus divides, giving rise to the tube nucleus and 
the nucleus of the generative cell. The latter immediately becomes 
surrounded by a ‘Hautschicht’. 
Soon after the renewal of activity the. following spring the 
nucleus of the generative cell divides, forming the stalk nucleus 
and the body cell nucleus. The latter becomes invested with a 
definite membrane, but a true stalk cell is never formed. 
By the time the pollen tube enters the archegonium chamber 
the body cell has attained a diameter of about 60 ju. • 
The division of the body cell takes place about three days 
before fertilization and usually results in the formation of two male 
cells equal in volume and bounded by definite membranes. The 
spindle of this division is of intra-nuclear origin. 
Several instances were found where three or four male cells 
had been produced by the division of one body cell, but it is prob¬ 
able that no more than two are ever functional. 
The ovulate buds first become distinguishable from vegetative 
buds a few weeks before pollination. 
The archesporium is derived from the cells in the lower 
portion of the nucellus and is recognizable at the time of pollination, 
but it is impossible to distinguish the megaspore mother cell until 
the following spring. 
Generally only one of the archesporial cells becomes a true 
mother cell, but occasionally as many as three may function as 
such. The non-functional cells give rise to the tapetum. 
Tetrad fformation takes place late in April. As a rule but 
one of the nuclei resulting from the heterotypic division undergoes 
the homotypic division. 
The nucleus of the functional megaspore becomes separated 
from the other nuclei in the mother cell by a membrane. 
The development of the female gametophyte occupies about 
six weeks. 
The megaspore membrane consists of two distinct layers. 
