Page:Popular Science Monthly Volume 82.djvu/239

Rh spikelets grown together; the same part in teosinte consists of bundles of distinct two-rowed spikelets with jointed axes. It takes two steps to bring maize to something like this condition. Ordinary maize varieties often produce individuals that have ears branched in much the same manner as the tassel or male spike. This is probably a reversion toward a former type. At least, pure varieties of this kind can be isolated. Furthermore it can be shown by crossing that the branched condition is due to a single hereditary character that has been lost by the cultivated kinds. The other step is the increase in number of rows, giving us the fine ears with from 18 to 24 rows that take the prizes in the agricultural shows. This feature is probably not due to the growing together of the spikelets. It is much more likely that increased number of parts came about through progressive variations, much as the increase of petals has brought the horticulturist so many double flowers. This type of variation is very common and still continues in maize, for the prize ears of the exhibitions contain many more rows than the more ancient little flints that were grown by the east coast red men.

The fact that but two essential variations, kinds that continue to occur, separate teosinte from the maize nearest like it, combined with the fact that the two are fertile in crosses lead me to believe that the two plants are simply diverse types of the same polymorphic aggregation, although they may be called species if one desires.

Perhaps we should stop here and not follow the path of speculation to its uttermost limit; still there are two more backward steps indicated by studying the cultivated plant. The plant is monœcious; that is, the male organs and the female organs are borne in separate flowers, though both are found on the same plant. This condition is not uncommon among the grasses although it is not the primitive condition. The unique fact is that the female flowers that form the ears are borne on short branches in the axils of the leaves of the maize stalk, while the male flowers are borne in a terminal spike, the tassel. This method of flowering is not so peculiar if the ear branch is examined. The husks that surround the ear are merely the leaves of the lateral branch upon which the ear is borne as a terminal spike. The lateral branch has simply shortened. It is telescoped together until the distance between the nodes is sometimes not more than an eighth of an inch. It seems just to conclude from the number of these internodes that the ear branch was at one time as long as that portion of the main stalk above the ear, that the flower spikes of the ancestral plant were once more or less level topped, bringing them into a horizontal plane. What caused the change