GERMINATION OF HIPPURIS VULGARIS. 447 
ones have 3 or 4. From an examination of some 50 seedlings it would 
appear that these numbers are rather arbitrary. Taking into consideration 
only the first, second, and third whorls, by far the most common formation 1s 
one of 4 leaves. The number may be, and often is, anything from 2 to 5, 
but 4 predominates. With this formation a definite leaf mosaic is obtained. 
the leaves of alternate whorls lying immediately above one another. It also 
appears that the whorls, at any rate in young seedlings, are the resalt of 
successive decussate leaf pairs with alternately very long and very short 
internodes. In older plants, and in the upper shoots, this arrangement is 
modified, and the whorls consist of from 6 to 10 leaves. 
The growth of the young plant has now been described up to the appear- 
ance of the fourth whorl of leaves. Shortly after this stage the first pair of 
lateral shoots appear in the axils of the cotyledons. At a slightly earlier 
stage many of the seedlings produce, also from the cotyledonary axils, a root 
which bends down and grows straight towards the mud. Branching of the 
primary root sometimes occurs, but appears to be a somewhat abnormal 
proceeding. The successive and opposite curvatures of the hypocotyl in the 
early stages deserves particular notice. 
There is considerable divergence of opinion as to the meaning and 
function of the ring of hairs produced at the collet. Warming (loe. cit.) 
discusses the subject shortly, and states that Klebs considers that their 
functions are absorption and anchorage. The former is very probable, but 
since the hairs are produced on the surface of the mud, the exact method of 
anchorage is difficult to understand. Samsoé Lund (in Bot. Tid. Copenhagen, 
Bd. v.) goes further, and, in the case of Batrachium heterophyllum, suggests 
that, by accumulating particles of mud, the hairs increase the weight of the 
seedling and prevent it from rising to the surface when the heavy empty 
fruit is dropped off. In the case of Hippuris the hairs do undoubtedly 
collect particles, and when the endocarps drop off the seedlings have a 
tendency to rise, but this is prevented not by the ring of hairs but by the 
penetration of the radicle, which is by then well developed, into the mud. 
Further, the horizontal spread of the hairs is such as to prevent penetration 
into the mud, and it seems that it is this prevention which is their chief 
mechanical function. Owing to the heaviness of the fruit lying on the mud, 
any growth of the hypocotyl is in the nature of a thrust away from the 
fruit. In the absence of the hairs, therefore, growth of the hypocotyl will 
lead simply to its penetration into the mud until only the fruit remains 
above. Under such circumstances the fruit can only be set free from the 
seedling by the withdrawal of the cotyledons under the mud, where their 
later functions would be impossible. It seems, therefore, that the function 
of the hair-ring is to form a platform or base away from which the upward 
growth of the shoot can take place, and by means of wbich the cotyledons 
can become erect and develop in their natural position, In the case of such 
LINN. JOURN.—BOTANY, VOL. XLVI. 21 
