Type of Har Average Row Number 
Half-tunicate 10.5 
Intermediate 112 
Fourth-tunicate 11.9 
Here, then, is another factor not previously recog- 
nized which is involved in the complex problem of row 
number in maize. It can now be said that, other things 
being equal, the lower the allele of Zu, the higher will 
be the number of rows on the ear. 
Rachis Tissue. It is a common observation both of 
practical farmers and students of maize that there is a 
great variation in the hardness or stiffness of individual 
cobs. Lenz (1948) has recently reported that the texture 
of the cob depends to a large extent upon the relative 
amount of heavily schlerenchymatized tissue. A_histo- 
logical examination of the nearly 500 cobs included in 
this study was out of the question, but it was possible to 
score the cobs with respect to the tissue of the rachis by 
testing with a dissecting needle the surface exposed 
when the cob was broken. The tissue immediately below 
the epidermis of the rachis was used for this purpose ; the 
cobs were classified as having spongy, horny or bony tis- 
sue. Bony cobs, such as would be expected from an in- 
trogression of ‘Tripsacum or teosinte, do not make their 
first appearance until Stratum III where they occur to 
the extent of three percent. The percentage of bony cobs 
reaches a maximum of 48 percent in Stratum V and falls 
off slightly to 88 percent in Stratum VI. 
Surface of Cupules. The alveoli or cupules in the ra- 
chis from which the paired spikelets arise vary consider- 
ably in the nature of their surfaces. Some are virtually 
glabrous, others are beset with short stiff hairs (hispid) 
and still others are lined with long slender hairs (hirsute). 
Glabrous and hirsute types occur in all strata, but cupules 
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