(4) When the lowermost tassel branch is modified as 
a husk-enclosed ‘‘sub-tassel ear,’’ as described by 
Galinat (1954 a), then a prophyll replaces the usual 
pulvinus. 
Prophyll development and the phytomer concept. Phy- 
tomer, as defined by Gray (1879), is a convenient term 
for describing the repetitious pattern which, in the 
grasses, consists of an internode, a leaf, a branch and a 
prophyll. When the vegetative phytomer is described 
in the order of maturation of parts, the leaf is placed at 
the top of an internode (Evans and Grover, 1940 and 
others). But in the inflorescence this order and the de- 
limitation of the phytomer appear to be different (Gali- 
nat, 19546) in that the spathe or its rudiment which 
subtends solitary or paired spikelets is borne at the base 
of a disarticulated phytomer. The concept of the phyto- 
mer as a discrete evolutionary unit has been rejected by 
Arber (1934) and others, although the term itself does 
appear to have value in characterizing the homologies of 
corresponding parts when the fundamental design is 
modified during floral development. 
In the floral phytomers' of most grasses, both spathes 
(subtending leaves) and prophylls have become either 
rudimentary or extremely modified except in the ulti- 
mate branches (florets) where the lemmas and paleas are 
their relics. The potentialities for complete development 
of all the parts in a floral phytomer remain, however, as 
is demonstrated by certain variations in the Maydeae and 
other tribes. For example, a homology between the lem- 
mas and vegetative leaves is readily shown by the con- 
version of the latter into the former in short-day maize 
and other grasses, as a result of certain sequences of 
photoperiodic treatment (Galinat and Naylor, 1951) or 
other disturbances which produce inflorescence prolifera- 
ry ee Par) . ° * Pp 
'The term *‘phytomer’’ will be used here only in a descriptive sense. 
[ 226 | 
