326 Nutrition and Selection. 
flowerheads of composites, and so forth. Every shoot 
has its cycle. It begins with simple or atavistic forms, 
then gradually manifests the characters which are pecu- 
liar to the species in their full development, and gradually 
reverts. From the primary shoot this cycle is transmitted 
to the secondary shoots and from these to the branches 
of still higher orders. In this process the latter may 
become stronger or weaker in comparison with the main 
shoot, or even of equal strength. As a rule the branches 
are weaker than the main shoot ; those which are not fall 
into two categories according to BRAUN, strengthened 
shoots and repeating shoots (Erstarkungssprosse and 
Wiederholungssprosse). 1 Spikes and racemes are the 
best known instances of weakened shoots ; their apical 
flowers, if such are present, are in advance of all the 
rest in their development as for instance in the peloric 
Digitalis. In the red clover the main shoot consists of 
a short upright rhizome, whereas the lateral branches 
gradually increase in strength and develop into flowering 
stems. In Tetragonia e.vpansa the main shoot is always 
short and erect, terminating with a flower. The secon- 
dary shoots often grow to more than a meter in length 
and are much stronger. Instances of strengthening 
shoots are the lateral branches which arise from the 
axils of the radical leaves of many plants (Ranunculus 
bulbosus}, or from the middle part of the stem (Chry- 
santhemum scgctum and Trifolium incarnatum) ; also 
the forked inflorescences as in Saponaria officinalis. Re- 
peating shoots are often runners, and then we have what 
BRAUN calls "repetitional generations," as in Valeriana 
officinalis, LysimacJiia vulgans, etc. 
See 23, p. 256. 
