COMPARISON OF FLOWER TYPES 293 
megaspores, thence to the formation of the immature gameto- 
phyte (embryo sac) with its egg, arrangement of cells and nuclei 
being noted. A slide should also be studied in which a young 
sporophyte is developing amid the cells representing the 
further growth of the gametophyte (i.e. the endosperm). 
The male gametophyte may also be studied in a prepared slide 
showing microspores (pollen cells) that have been germinated 
so as to show the tubular antherids (pollen tubes) and which 
should also show the antheridial nucleus, and the generative 
nucleus (or possibly the two non-ciliated sperms derived from 
it). 
(f) Strictly considered the fruits consist of the modified 
carpels containing the ripe seeds, but any accessory modification 
of adjacent parts should also be noted. Examine the flowers 
when the fruits are mature and note the structure of the carpels, 
whether dry or partly fleshy, and dehiscent (i.e. opening to per- 
mit the escape of the seeds) or not (indehiscent). Note (in 
Fragaria or Duchesnea) the considerable enlargement of the 
torus, and consequent separation of the carpels. Note how the 
calyx is modified, and whether it remains or falls. Remove a 
mature seed from a carpel and note its size and shape, and the 
external characters of the seed coat (consisting of the integu- 
ments); section it transversely and longitudinally and deter- 
mine the presence or absence of endosperm, the relative size 
of the embryo, and the number of cotyledons. 
530. If now we compare the three flowers described 
above it will be seen that they are very similar. Yet 
the Buttercup and Strawberry have their petals and 
sepals in whorls or series of five each, while they are in 
whorls of three each in the Water Plantain. Again in 
the former there are two rudimentary leaves (“cotyle- 
dons’’) on the embryo sporophyte, while in the latter 
there is but one. Now if we carry our comparison to the 
plants bearing the flowers we find other differences. The 
first leaves on the little plant in the Buttercup and the 
Strawberry as it appears above ground are opposite on the 
stem, while in the Water Plantain they are alternate, 
